The interactions between temozolomide and chloroquine were examined via Dispersion-Corrected Density Functional Theory and MP2 methods. Chloroquine was considered in both its lowest energy structure and in a local minimum where its aromatic system and secondary amine group are free to interact directly with temozolomide. The accessibility of these two components to intermolecular interaction makes the lowest energy dimer of this local monomer minimum competitive in total energy with that involving chloroquine's most stable monomer geometry. In either case, the most stable heterodimer places the aromatic ring systems of the two molecules parallel and directly above one another in a stacked geometry. Most of the local minima are also characterized by a stacked geometry as well. Comparison between B3LYP and B3LYP-D binding energies confirms dispersion is a primary factor in stabilizing these structures. © 2016 Wiley Periodicals, Inc.

Temozolomide and chloroquine each contain an aromatic system conjoined with appending groups capable of forming strong H-bonds. The most important factor in the structure of heterodimers is the dispersion force between the two stacked aromatic systems. The strong intermolecular H-bonds formed by a secondary minimum of the chloroquine monomer with temozolomide can favor this heterodimer over one including the global minimum of chloroquine.

We have compared the performances of the one-parameter and linearly scaled one-parameter double-hybrid density functionals (1DH-DFs and LS1DH-DFs) for noncovalent interactions. The only one parameter related to the Hartree–Fock (HF) exchange for each of the tested 1DH-DFs and LS1DH-DFs has been fitted with the well-designed S66 database. The obtained DHDFs are dubbed as 1DH-PBE-NC, LS1DH-PBE-NC, 1DH-TPSS-NC, LS1DH-TPSS-NC, 1DH-PWB95-NC, and LS1DH-PWB95-NC, where “NC” denotes noncovalent interactions. With a specific combination of exchange and correlation functionals, the dependent parameters related to the nonlocal second-order perturbative energies are nearly identical for the 1DH and LS1DH models. According to our benchmark computations against the S66, S22B, NCCE31, ADIM6, and L7 databases, we suggest that the 1DH-PWB95-NC and LS1DH-PWB95-NC functionals are much more suitable for evaluating noncovalent interaction energies. Unlike the versatile DHDFs with dispersion corrections for general purpose, our optimized 1DH-DFs and LS1DH-DFs only aim at noncovalent interactions. © 2016 Wiley Periodicals, Inc.

As fifth rung approaches in density functional theory, double-hybrid density functionals are seen as efficient methods for electronic structure computations. These functionals are potentially promising for the treatment of non-covalent interactions because they contain nonlocal second-order perturbative energy terms, although correction terms are still sometimes needed. A benchmark study of one-parameter and linearly scaled one-parameter double-hybrid density functionals suggests that 1DH-PWB95-NC and LS1DH-PWB95-NC are the more suitable of these approaches for studying non-covalent interactions.

Recently, the quantum harmonic oscillator model has been combined with maximally localized Wannier functions to account for long-range dispersion interactions in density functional theory calculations (Silvestrelli, J. Chem. Phys. 2013, 139, 054106). Here, we present a new, improved set of values for the three parameters involved in this scheme. To test the new parameter set we have computed the potential energy curves for various systems, including an isolated Ar2 dimer, two N2 dimers interacting within different configurations, and a water molecule physisorbed on pristine graphene. While the original set of parameters generally overestimates the interaction energies and underestimates the equilibrium distances, the new parameterization substantially improves the agreement with experimental and theoretical reference values. © 2016 Wiley Periodicals, Inc.

A new parametrization for the quantum harmonic oscillator model to compute corrections due to the van der Waals interactions in density functional theory is proposed in this work. It is demonstrated that the improved parametrization substantially improves the agreement with experimental and theoretical reference values. Due to the fact that the present scheme can be seamlessly integrated into existing electronic structure codes, this development open the door to routinely compute the van der Waals interactions in the framework of density functional theory calculations.

Signal processing techniques have been developed that use different strategies to bypass the Nyquist sampling theorem in order to recover more information than a traditional discrete Fourier transform. Here we examine three such methods: filter diagonalization, compressed sensing, and super-resolution. We apply them to a broad range of signal forms commonly found in science and engineering in order to discover when and how each method can be used most profitably. We find that filter diagonalization provides the best results for Lorentzian signals, while compressed sensing and super-resolution perform better for arbitrary signals. © 2016 Wiley Periodicals, Inc.

Three methods for reconstructing a signal, e.g. in NMR, that beat the Nyquist limit in presence of prior information are discussed in terms of their successes, failures and characteristics. Compress sensing, super-resolution, and filter diagonalization are modern signal processing algorithms, but, despite their potential, they have not been yet widely adopted in chemistry.

We provide quantum chemical insights into curcumin's prevention of Alzheimer' disease through curcumin's scavenging of neurotoxic Cu(II), Zn(II), and Pd(II) transition metal ions that catalyze polymerization of amyloid-β and promote misfolding of amyloid into neurotoxic conformations. We have employed high level quantum chemical computations to study the chelate complexes of curcumin with Cu(II), Zn(II), and Pd(II). Quantum chemically derived structures, IR spectra, and UV-visible spectra of these complexes corroborate with the observed spectra, confirming that the primary site of chelation is the β-diketone bridge through the loss of an enolic proton of curcumin. We have also obtained the various structural parameters such as the Mulliken charges on various centers, highest occupied, lowest unoccupied molecular orbitals—all of which confirm that curcumin forms chelate complexes and thus acts as a scavenger of these neurotoxic metal ions preventing Alzheimer's disease. We find that the open-d-shell Cu(II) and Pd(II) form nearly square planar complexes while the closed-d-shell Zn(II) forms a tetrahedral complex with curcumin. © 2016 Wiley Periodicals, Inc.

Quantum chemical insights into Alzheimer's disease is presented. It is shown that curcumin scavenges neurotoxic Cu(II), Zn(II), and Pd(II) ions that catalyze polymerization and misfolding of amyloid-β protein through chelation as a mechanism for the prevention of Alzheimer's disease.

The computation of high-harmonic generation spectra by means of Gaussian basis sets in approaches propagating the time-dependent Schrödinger equation was explored. The efficiency of Gaussian functions specifically designed for the description of the continuum proposed by Kaufmann *et al*. (J Phys B 1989, 22, 2223) was investigated. The range of applicability of this approach was assessed by studying the hydrogen atom, that is, the simplest atom for which “exact” calculations on a grid could be performed. The effect of increasing the basis set cardinal number, the number of diffuse basis functions, and the number of Gaussian pseudo-continuum basis functions for various laser parameters was notably studied. The results showed that the latter significantly improved the description of the low-lying continuum states, and provided a satisfactory agreement with grid calculations for laser wavelengths *λ*_{0} = 800 and 1064 nm. The Kaufmann continuum functions, therefore, appeared as a promising way of constructing Gaussian basis sets for studying molecular electron dynamics in strong laser fields using time-dependent quantum-chemistry approaches. © 2016 Wiley Periodicals, Inc.

High-harmonic generation (HHG) is a highly nonlinear phenomenon which provides coherent XUV and soft X-ray radiation with attosecond (10^{−18} s) duration. HHG is also a powerful tool for studying atomic and molecular structures, combining a short temporal resolution with a high spatial resolution. HHG is characterized by electron excursion in the continuum. Electron dynamics is studied by means of the time-dependent Schrödinger equation using optimal Gaussian functions for the representation of the continuum states.

A concept for the interactions between π-systems is necessary to understand a number of phenomena in modern material sciences such as supramolecular properties and self-assembly. In the present article, we investigate the intermolecular interaction energies between organic semiconductors with extended π-systems using SAPT (symmetry-adapted perturbation theory), LMO-EDA (localized molecular orbital energy decomposition analysis), DFT-D (density functional theory including dispersion corrections), and force-field approaches. Both apolar organic molecules such as acenes and highly polarized π-systems of merocyanines and squaraines were used to probe the influence of electrostatics on the shape of the potential energy surfaces (PES) governing the geometric structures of aggregates. Our results reveal that the shapes of the PESs result from variations in the short-range, highly specific repulsion forces even for highly polar molecules. Using distributed quadrupoles, we show that it is nevertheless possible to mimic the intermolecular potentials with electrostatics. This is also possible with van-der-Waals potentials and a simple overlap-based force-field ansatz based on the overlap between p-orbitals. © 2016 Wiley Periodicals, Inc.

Interactions between π-systems are of major importance for a number of phenomena, such as supramolecular properties of organic semiconductors and molecular self-assembly in modern material sciences. Employing high-level SAPT, LMOEDA, and DFT-D calculations, this work demonstrates that the repulsion energy between monomers gives rise to characteristic features of the intermolecular potential energy surfaces. Electrostatic, van der Waals interactions, and overlap-based approaches can be used to mimic features of the intermolecular potential.

The nature of E···E' bonding in homonuclear (E = E') and heteronuclear (E ≠ E') [Nap(EPh)(E'Ph)]^{•+} (E, E' = O, S, Se, and Te) radical cations has been investigated by quantum chemistry and the topological analysis of electron density. The calculation results show that the E···E' bonding in the title compounds occurs through attractive interactions; O···E' (E'=O, S, Se, and Te) bonding are electrostatic interactions, and the others have a partial covalent character. The nature of E···E' bonding varies periodically, with the changes of E' atoms going from the lighter to the heavier (O, S, Se, and Te). Both in homonuclear and heteronuclear [Nap(EPh)(E'Ph)]^{•+}, for the same E atom, a heavier E' atom means stronger E···E/E' bonding, a more covalent character of the E···E' bond, and more spin electron density transfers from benzene rings to the E···E' group. © 2016 Wiley Periodicals, Inc.

Some sulfur radical cations contain a two center-three-electron (2c-3e) σ-bond, also known as ‘hemibond’. These 2c-3e σ-bonded radicals are characterized by a relatively weak bond between the two atoms. The geometry of model radicals and the nature of E…E' bonding in them is investigated *in silico*. The geometry and E…E' bonding varies periodically with the changes of E' atoms going from the lighter to the heavier (O, S, Se, and Te).

New medium size Gaussian-type basis set R-ORP for evaluation of static and dynamic electric properties in molecular systems is presented. It is obtained in a close resemblance to the original ORP basis set, from the source basis set through addition of two first-order polarization functions whose exponent values are optimized with respect to the finite field restricted open-shell Hartree–Fock (ROHF) atomic polarizabilities. As the source set the VTZ basis set of Ahlrichs and coworkers, augmented with additional diffuse functions and contracted to the form [6s/3s] for hydrogen and [11s7p/4s3p] for carbon through fluorine, is chosen. The resulting basis set is of the form [6s2p/3s2p] for hydrogen and [11s7p2d/4s3p2d] for other atoms. Presented basis set is next tested in the CCSD static and dynamic molecular polarizability and hyperpolarizability calculations for a set of ten and four test molecules, respectively, for which very accurate reference data exist. Additionally, the recently developed ORP basis set is employed in the calculations to examine the limits of its applicability. Results are compared to the literature data obtained in both, large and diffuse, as well as reduced-size basis sets. In the case of polarizability calculations, the aug-pc-1 and R-ORP are the optimal choices among the investigated smaller basis sets, with the overall performance of the aug-pc-1 set being better. Among the larger sets, the ORP performs better in the case of average polarizability, while the RMSE values for polarizability anisotropy are practically identical for d-aug-cc-pVDZ and ORP sets. Finally, the R-ORP and ORP basis sets compete other small bases in the evaluation of the first hyperpolarizability in investigated systems. © 2016 Wiley Periodicals, Inc.

New polarized R-ORP basis set for evaluation of static and dynamic electric properties in molecular systems is developed and tested in calculation of polarizability and first hyperpolarizability of test systems together with the recently developed ORP basis set. Both sets are valuable alternative to traditional basis sets in the evaluation of first hyperpolarizability.

An *in silico* study is performed on the structure and the stability of noble gas (Ng) bound MO complexes (M = Cu, Ag, Au). To understand the stability of these Ng bound complexes, dissociation energies, dissociation enthalpy, and dissociation free energy change are computed. The stability of NgMO is also compared with that of the experimentally detected NgMX (X= F, Cl, Br). It is found that MO has lower Ng binding ability than that of MX. All the dissociation processes producing Ng and MO are endothermic in nature and for the Kr-Rn bound MO (M = Cu, Au), and Xe and Rn bound AgO cases, the corresponding dissociation processes are turned out to be endergonic in nature at standard state. The Wiberg bond indices of NgM bonds and NgM electron transfer gradually increase from Ar to Rn and for the same Ng they follow the order of NgAuO > NgCuO > NgAgO. Energy decomposition analysis shows that the NgM bonds in NgMO are partly covalent and partly electrostatic in nature. Electron density analysis further highlights the partial covalent character in NgM bonds. © 2016 Wiley Periodicals, Inc.

The nature of the interaction between noble metals and noble gasses has been at the center of a lively debate. The noble gas binding ability of noble metal (Cu, Ag, Au) oxides is explored by employing high-level *ab initio* methods. The stability of noble gas bound metal oxides are very comparable to that of experimentally detected noble gas bound noble metal halides.

Many fermions Kramers pairs formalism is considered from the prospective of the sum of individual single fermion time-reversal operators. The obtained many fermions “pseudo Kramers pairs operator” ( ), as well as its square ( ), have formally the same structure as the many fermion spin operators and . Nevertheless, the shape of eigenfunctions with respect to and is different. Herein all Kramers adapted eigenfunctions of for cases of up to four unpaired fermions are compiled, and their properties with respect to further advocated. It will be shown that degeneracy of the multiplets recovers the proper behavior with respect to Pascal's triangle. A projection operator for obtaining the “high spin” Kramers adapted eigenfunctions is suggested. Noncommutation of with spin and angular momentum operators and degeneracy is discussed at last. © 2016 Wiley Periodicals, Inc.

Pseudo Kramers symmetry is introduced upon spin additivity. Eigenfunctions of pseudo Kramers operator squared are presented for cases with up to four unpaired fermions. Eigenvalues of the pseudo Kramers operator squared correlate directly with the number of open shells. The obtained pseudo Kramers symmetry functions have the degeneracy closely related to coefficients in Pascal's triangle.

Working from the arrangements of both row and group numbers developed within Mendeleev's periodic table of elements, periodic trends can be shown to exist in many constants of triatomic molecules: an extension of the Periodic Law for atoms to the realm of molecules. Trends are identified for vibrational frequencies, bond lengths, and to a lesser extent interior angles. This work includes empirical sources for such data, supplemented with calculations using diatomic analogs where possible. Otherwise, computation is used for all possible configurations of row two and row three main-group elements to both corroborate and extend empirical results. Organization of this data into a detailed, highly symmetric, multidimensional coordinate system allows for robust graphical and statistical analysis of all constants and associated trends, which in turn permits rapid identification of suspect data to be rechecked. All collected empirical and computational data, along with several interactive visualizations highlighting these results, is available online. © 2016 Wiley Periodicals, Inc.

This work shows there exists periodic behavior across all triatomic molecules in consideration of their vibrational frequencies, and to a lesser extent their bond lengths and angles, as compiled from both experimental studies and computational simulations. A Mendeleevian numbering scheme of group/row number coordinates to make a highly-symmetric, 13-dimensional form is used. These results restate the Periodic Law in a molecular rather than elemental sense, a satisfying but not necessarily expected result, given quantum mechanical complexity.

We study a wavepacket tunneling in one-dimensional periodically driven double-well system using entangled trajectory molecular dynamics method. The tunneling dynamics dependents on the amplitude and frequency of the driven force are present. Both resonant and nonresonant tunneling process are enhanced by the driven force when the system is chaotic under classical dynamics. We give entangled trajectory in phase space compared to corresponding classical trajectory with same initial state to visually show quantum tunneling process. The average values of quantum tunneling probability after long time evolution have been shown in the parameter spaces, the effect of resonance and chaos on the tunneling dynamics are present. The relation between chaos and the uncertainly product is discussed in the end. © 2016 Wiley Periodicals, Inc.

Wavepacket tunneling in one-dimensional, periodically driven doublewell system, can be efficiently studied using entangled trajectory molecular dynamics method. Tunneling dynamics depends on the amplitude and frequency of the driven force, when the system is chaotic under classical dynamics. Chaos is found to enhance both resonant and non-resonant tunneling processes. The increase of the perturbation strength enhances the increment of the quantum fluctuation in the case of same frequency.

Quantum mechanical exchange effects in purely organic *N*,*N*′-dioxy-2,6-diazaadamantane biradical derivatives with promesogenic substituents have been studied. To determine intermolecular exchange energies, packing conditions of the radical core units in layered liquid crystalline phases are simulated using the Gaussian 09 program. The broken symmetry approach gives J ≈ 7 cm^{−1} for intramolecular ferromagnetic exchange interactions between nitroxyl radical centers in one molecule. Both ferromagnetic and antiferromagnetic intermolecular interactions are possible in this kind of systems according to the obtained calculation results. Depending on the mutual positioning and orientation of molecules, the intermolecular antiferromagnetic exchange constant can reach a value of −50 cm^{−1}, and the intermolecular ferromagnetic constant a value of 10 cm^{−1}. The simultaneous presence of intramolecular and intermolecular exchange between spin-carrying centers in this kind of supramolecularly ordered multispin systems is favorable for the formation of magnetically interacting chains and two-dimensional networks. © 2016 Wiley Periodicals, Inc.

Organic ferromagnetic materials, based on organic compounds containing stable free radicals, have been theoretically suggested for subsequent synthesis. The effects of liquid crystalline supramolecular organization and, possibly, ferroelectric ordering on the magnetic properties of organic radicals are currently subjects of considerable interest. Liquid crystalline order in *N*,*N*′-dioxy-2,6-diazaadamantane biradicals can lead to the both ferromagnetically and antiferromagnetically coupled chains and networks, as shown by quantum-chemical calculations.

Solid-state NMR spectroscopy and computational approaches such as Molecular Dynamics (MD) simulations and Density Functional Theory have proven to be very useful and versatile techniques for studying the structure and the dynamics of noncrystalline materials if a direct comparison between experiment and theory is established. In this review, the basic concepts in first-principle modeling of solid-state NMR spectra of oxide glasses are presented. There are three theoretical ingredients in the computational recipe. First, classical or *ab initio* molecular dynamics simulations are employed to generate the structural models of the glasses of interest. Second, periodic Density Functional Theory calculations coupled with the gauge including projector augmented-wave (GIPAW) algorithm form the basis for the *ab initio* calculations of NMR parameters (chemical shielding and quadrupolar parameters). Finally, Spin-effective Hamiltonian are employed to simulate the solid-state NMR spectra directly comparable with the experimental counterparts. As an example of this methodology, the investigation of the local and medium range structure of Na-Ca silicate and aluminosilicate glasses that are usually employed as simplified models for basaltic, andesitic and rhyolitic magmas will be reported. We will show how the direct comparison of the theoretical NMR spectra of MD derived structural models with the experimental counterparts allows gaining new insights into the atomistic structure of very complex oxide glasses. © 2016 Wiley Periodicals, Inc.

Molecular dynamics simulations coupled with DFT-GIPAW NMR calculations and spin-effective Hamiltonians provide a clear view of the local and medium range structure of multicomponent alumina silicate glasses.

The nature of the bonding interactions including the intramolecular SS interactions in tetrasulfur tetranitride, S_{4}N_{4} are probed by performing very large amplitude vibrations of all of the 18 normal modes of vibration. The QTAIM and stress tensor point properties are -then investigated and found to be highly dependent on the mode of vibration. A considerable degree of metallicity ξ(**r**_{b}) is found for the SS and SN bonding interactions. A unique bonding feature is found for a small amplitude vibration of the most anharmonic mode of this investigation, mode 2, where the SS bond critical point (BCP) transforms from a closed-shell SS BCP to a shared-shell SS BCP. We find 17 new unique QTAIM topologies for the molecular graphs corresponding to the 18 modes of vibration along with seven “missing” topologies that are mapped onto a spanning 2-D Quantum topology Phase Diagram (QTPD). In addition, eleven unique topologies existing on 3-D QTPDs are found due to the presence of non-nuclear attractors (NNAs). We use the stress tensor eigenvalues to explain the invariance of the numbers and types of QTAIM critical points. The applicability of both the stiffness *S* and stress tensor stiffness *S*_{σ} are also explored. Two new bond measures are introduced, a polarizability *P* and the stress tensor polarizability *P*_{σ} which are derived from the stiffness *S* and stress tensor stiffness *S*_{σ}, respectively. © 2016 Wiley Periodicals, Inc.

Tetrasulfur tetranitride, S_{4}N_{4} can form a large number of compounds that have been experimentally obtained, including the long chain polymeric sulfur nitride and a variety of small molecules produced from the polymer. The structural flexibility of the molecule is one of the most important factors affecting the reactivity of S_{4}N_{4.} The QTAIM and stress tensor point properties are found to be highly dependent on the mode of vibration of the molecules.

A DFT study was carried out on the ground state structures of ternary Cu_{l}Ag_{m}Au_{n} (*l* + *m* + *n* = 6) clusters, with the aim of investigating changes of thermal and kinetic stabilities as an effect of composition, as well as the composition dependence of the electrostatic potential, of stable planar structures. DFT optimizations were performed using the PBE functional and the SDD basis set. All the optimized structures adopt planar geometries with bent triangular structures. Calculated binding energy values are in the range 1.5–1.9 eV/atom, which shows their thermal stability. The predicted HOMO-LUMO energy gap values are in the semiconductor region, providing a qualitative indication of a moderate kinetic stability. NBO analyses indicate the existence of two mechanisms promoting planar structural stability, one due to bonding-antibonding orbital interaction, and the other one due to the well-known spd hybridization. Wiberg indices were obtained showing interatomic bonding. Electrostatic potential calculations show the existence of nucleophilic attack regions preferentially around silver and copper atoms located at the vertices while electrophilic attack regions are found in the vicinity of gold atoms over the cluster plane. Apparently, charge transfer occurs toward gold from silver and copper atoms when the concentration is favorable in the proximity of gold atoms. In particular, if the small ternary clusters discussed here contain only one gold atom, then a high electron density is observed at the site of this gold atom. © 2016 Wiley Periodicals, Inc.

Density Functional Theory calculations elucidate the structure of 6-atom ternary noble metal clusters. As similarly seen in the case of small bimetallic clusters, planar structures are found, with an energy gap consistent with semiconductor nanoparticles. The planarity of the ground state structures thus obtained is analyzed through the natural bond orbital scheme, and the electrostatic potential at different atomic sites is obtained to be employed as a reactivity descriptor.

We have performed the first-principles calculations on the structural, electronic, and magnetic properties of 3d transition-metal™ (Cr, Mn, Fe, Co, and Ni) atoms doped 2D GaN nanosheet. The results show that 3d TM atom substituting one Ga leads to a structural reconstruction around the 3d TM impurity compared to the pristine GaN nanosheet. The doping of TM atom can induce magnetic moments, which are mainly located on the 3d TM atom and its nearest-neighbor N atoms. It is found that Mn- and Ni-doped GaN nanosheet with 100% spin polarization characters seem to be good candidates for spintronic applications. When two Ga atoms are substituted by two TM dopants, the ferromagnetic (FM) ordering becomes energetically more favorable for Cr-, Mn-, and Ni-doped GaN nanosheet with different distances of two TM atoms. On the contrary, the antiferromagnetic (AFM) ordering is energetically more favorable for Fe-doped GaN nanosheet. In addition, our GGA + *U* calculations show the similar results with GGA calculations. © 2016 Wiley Periodicals, Inc.

Although 2D gallium nitride (GaN) nanosheets are non-magnetic, their doping with 3d transition metal atoms (Cr, Mn, Fe, Co, and Ni) can induce magnetization. The magnetic properties of 2D GaN-based diluted magnetic semiconductors mainly originate from the 3d electrons of the transition atoms. Theoretical calculations suggest that the 3d metal-doped GaN nanosheet maybe be used successfully as spintronic and magnetic data storage materials.

We have studied how ReaxFF and Behler–Parrinello neural network (BPNN) atomistic potentials should be trained to be accurate and tractable across multiple structural regimes of Au as a representative example of a single-component material. We trained these potentials using subsets of 9,972 Kohn-Sham density functional theory calculations and then validated their predictions against the untrained data. Our best ReaxFF potential was trained from 848 data points and could reliably predict surface and bulk data; however, it was substantially less accurate for molecular clusters of 126 atoms or fewer. Training the ReaxFF potential to more data also resulted in overfitting and lower accuracy. In contrast, BPNN could be fit to 9,734 calculations, and this potential performed comparably or better than ReaxFF across all regimes. However, the BPNN potential in this implementation brings significantly higher computational cost. © 2016 Wiley Periodicals, Inc.

ReaxFF, and the Behler-Parrinello neural network (BPNN) atomistic potential were trained from density functional theory calculations to be accurate and tractable across multiple structural regimes of Au. We found that the BPNN potential can be trained from much larger training sets to perform comparably or significantly better than ReaxFF across all regimes. However, in the implementation used in this work, the BPNN potential also brings significantly higher computational cost.

The optimal exponent *α* values (*α*_{opt}) in *s*-type Gaussian-type functions (GTFs) for quantum protons and deuterons, which are used for multicomponent molecular orbital calculations including nuclear quantum nature of protons and deuterons, are analyzed for several charged or polarized systems and their deuterated species. Ishimoto and coworkers (Ishimoto, Int. J. Quantum Chem. **2006**, 106, 1465) have already proposed the average exponent values for five neutral molecules (*α*_{ave}), and demonstrated that their *α*_{ave} enables us to evaluate the H/D isotope effect on energies and geometries of various neutral species. The differences between total energies of several charged or polarized systems with previous *α*_{ave} and our *α*_{opt} correspond to only less than 0.004% of the total energy (0.47 kcal·mol^{−1}) except for HeH^{+} and HeD^{+} molecules, while the difference between interaction energies of H_{2}OH^{+…}OH_{2} and H_{2}OD^{+…}OH_{2} systems with previous *α*_{ave} is 19% (0.22 kcal·mol^{−1}) smaller than that with our *α*_{opt}. Meanwhile, the difference between OH bond lengths in H_{2}OH^{+…}OH_{2} system with *α*_{ave} and *α*_{opt} values is 0.027 Å. We also found that the interaction energies with *α*_{opt} value at the geometry optimized with previous *α*_{ave} value (*α*_{sp}) well reproduce those at the geometry optimized with *α*_{opt} value. We have demonstrated that the nuclear basis functions based on *s*-type GTFs with previous *α*_{ave} values enable us to evaluate the H/D isotope effect on energies and geometries of charged or polarized systems. © 2016 Wiley Periodicals, Inc.

The optimal exponent *α* values in Gaussian-type function for quantum protons and deuterons, which are used for multicomponent molecular orbital calculations in charged or polarized systems are systematically analyzed. The H/D isotope effect on total energies and geometries of charged or polarized systems are adequately evaluated with the average *α* values for five neutral molecules. The H/D isotope effect on interaction energies in charged hydrogen-bonded systems are also analyzed.

This DFT study examined the interaction of a sulfated zirconia (SZ) slab model system (heterogeneous catalyst) and triacetin (a precursor in biodiesel production) using explicit methanol solvent molecules. Full geometry optimizations of the systems were performed at the B3LYP level of theory. Gibbs free energies provide insight into the spontaneity of the reactions along a three-step reaction mechanism for the transesterification of triacetin. Charge decomposition analysis revealed electronic charge transfer between the metallic oxide and the organic moieties involved in the reaction mechanism. Fukui indices indicate the likely locations on the SZ surface where catalysis may occur. The quadratic synchronous transit scheme was used to locate transition structures for each step of the transesterification process. The results are in agreement with the strongly acidic catalytic character of zirconium observed experimentally in the production of biodiesel. © 2016 Wiley Periodicals, Inc.

Biodiesel is seen as an environmentally sustainable alternative to the use of fossil fuels. The reaction mechanism and charge transfer of triacetin, a precursor in biodiesel production, on sulfated zirconia as a heterogeneous catalyst can be analyzed using computational chemistry techniques. The study provides an insight on the catalytic properties of sulfated zirconia and its role on the transesterification of triacetin.

CO adsorption and oxidation over supported Pt_{14} with different CO coverage on TiO_{2}(110) surface were investigated using density functional theory (DFT) calculations and thermodynamic analysis. According to the phase diagram, Pt_{14}/TiO_{2}(110) and 11CO@Pt_{14}/TiO_{2}(110) were chosen to represent the low and high CO coverage of Pt clusters, respectively. Our study shows that the high coverage of CO can induce the structural change of supported Pt clusters and weaken the interaction between Pt clusters and TiO_{2} support. The CO adsorption and oxidation mechanism depends on the CO coverage, which is determined by the experimental reactant composition, pressure, and temperature. At low CO coverage, the dissociated oxygen is active specie to form CO_{2} by reacting with CO. At high coverage, the molecular oxygen can directly react with CO via the formation of OOCO intermediate. Our proposed mechanisms provide useful information for understanding the CO oxidation over Pt clusters with different CO coverage. © 2016 Wiley Periodicals, Inc.

The CO adsorption and oxidation mechanism depends on the CO coverage, which is determined by the experimentally reactant composition, pressure and temperature. At low CO coverage, the dissociated oxygen is active specie to form CO_{2} by reacting with CO. At high coverage, the molecular oxygen can directly react with CO via the formation of OOCO intermediate.

New group 10 metalloorganic complexes are proposed as the basis of new catalysts for the formation of carbon-phosphorous bonds. Density functional theory (DFT) is applied, using multiple DFT functionals, to model molecular geometry as well as electron density distribution in the highest occupied molecular orbitals (HOMOs) expected to carry out a reductive catalytic cycle. DFT/M06 analysis predicts a robust planar geometry, regardless of alteration of major components. Precursors for rapid catalyst generation should begin with an electron-withdrawing monodentate ligand. Palladium and platinum catalysts have lower chemical hardness, but the electron distribution in the HOMO of the nickel-based catalyst is preferred for reductive catalytic mechanisms. Both electron density and chemical hardness, however, are affected by the choice of metal ion and the composition of the monodentate ligand bound to it. Group 10 metalloorganic complexes are modeled as precursors for generating new catalysts for a minimally wasteful method of forming bonds commonly found in biochemically active compounds. Suitable precursors have an accessible metal center, as well as significant the HOMO/LUMO involvement at the metal center. All complexes studied offer similar geometries, but precursor transformation into catalyst depends on the electron-withdrawing ligand being exchanged. Catalyst turn over number is predicted to depend primarily on the central metal. © 2016 Wiley Periodicals, Inc.

Group 10 metalloorganic complexes are modeled as precursors for generating new catalysts for a minimally wasteful method of forming bonds commonly found in biochemically-active compounds. Suitable precursors have an accessible metal center, as well as significant HOMO/LUMO involvement at the metal center. All complexes studied offer similar geometries, but precursor transformation into catalyst depends on the electron withdrawing ligand being exchanged. Catalyst turn over number is predicted to depend primarily on the central metal.

Critical parameters in three screened potentials, namely, Hulthén, Yukawa, and exponential cosine screened Coulomb potential are reported. Accurate estimates of these parameters are given for each of these potentials, for all states having
. Comparison with literature results is made, wherever possible. Present values compare excellently with reference values; for higher *n*, *ℓ*, our results are slightly better. Some of these are presented for first time. Further, we investigate the spherical confinement of H atom embedded in a dense plasma modeled by an exponential cosine screened potential. Accurate energies along with their variation with respect to box size and screening parameter are calculated and compared with reference results in literature. Sample dipole polarizabilities are also provided in this case. The generalized pseudospectral method is used for accurate determination of eigenvalues and eigenfunctions for all calculations. © 2016 Wiley Periodicals, Inc.

Critical parameters for three screened Coulomb potentials, namely, Hulthén, Yukawa, and ECSC potential, can be accurately estimated. For this purpose the GPS method is employed, because it has been demonstrated to produce quite reliable and accurate results for a variety of physically and chemically important systems, including quantum confinement. The ECSC potential is then used to investigate spherical confinement of an H atom embedded in dense plasma.

In quantum theory, solving Schrödinger equation analytically for larger atomic and molecular systems with cluster of electrons and nuclei persists to be a tortuous challenge. Here, we consider, Schrödinger equation in arbitrary N-dimensional space corresponding to inverse-power law potential function originating from a multitude of interactions participating in a many-electron quantum system for exact solution within the framework of Frobenius method via the formulation of an ansatz to the hyper-radial wave function. Analytical expressions for energy spectra, and hyper-radial wave functions in terms of known coefficients of inverse-power potential function, and wave function parameters have been obtained. A generalized two-term recurrence relation for power series expansion coefficients has been established. © 2016 Wiley Periodicals, Inc.

Obtaining an analytical solution to the Schrödinger equation for a many-electron quantum system, in a multi-dimensional space is challenging because of the multitude of interactions involved, that add up to nearly a unsolvable mathematical complexity. A mathematical formalism has been developed to solve the Schrödinger equation in N-dimensional space for inverse-power law potential function arising from such interactions, within the framework of Frobenius method via the formulation of an ansatz to the hyper-radial wave function.

We discuss the method to compute the integrals, which appear in the retarded potential term for a real-time simulation based on quantum electrodynamics. We show that the oscillatory integrals over the infinite interval involved in them can be efficiently performed by the method developed by Ooura and Mori based on the double exponential formula. © 2016 Wiley Periodicals, Inc.

Electromagnetic interactions are not transmitted instantaneously. They travel with a finite speed, which equals the speed of light. This is common in relativistic field theory and quantum electrodynamics is no exception. This effect is encapsulated in the retarded potential, where contributions in past time are integrated over consistently with the finite speed of the interaction. This article discusses a method to perform such a complicated integration efficiently.

Local physical quantities for spin are investigated on the basis of the four- and two-component relativistic quantum theory. In the quantum field theory, local physical quantities for spin such as the spin angular momentum density, spin torque density, zeta force density, and zeta potential play important roles in spin dynamics. We discuss how to calculate these local physical quantities based on the two-component relativistic quantum theory. Some different types of relativistic numerical calculations of local physical quantities in Li atom and C_{6}H_{6} are demonstrated and compared. Local physical quantities for each orbital are also discussed, and it is seen that a total local zeta potential is given as a result of some cancellation of large contributions from each orbital. © 2016 Wiley Periodicals, Inc.

Local physical quantities for spin based on the quantum field theory play important roles in spin dynamics. The numerical results of these quantities based on the four- and two-component relativistic quantum theory reveal the relativistic interaction can have a great influence on the local physical quantities, even if it has little effect on the orbital energies.

We have performed first-principle density functional theory calculations to investigate O_{2} dissociation on Pt(111) surface. A stepwise mechanism has been proposed. First, the adsorbed O_{2} dissociate into two oxygen atoms to get adsorbed on the nearby adsorption sites. Then, oxygen atoms further migrate to other more stable adsorption sites. The influence of solvent water on oxygen dissociation was also examined. The results show that the co-adsorption of water has little impact on O_{2} dissociation. However, when water participates in the reaction, the energy barriers were reduced greatly. These results have very important significance to understand the mechanism of oxygen reduction. © 2016 Wiley Periodicals, Inc.

Density functional theory calculations provide insight into the stepwise dissociation pathways of O_{2} on a Pt(111) surface. Calculations reveal that water co-adsorption has little influence on dissociation. However, dissociation is facilitated when water molecules participate in the reaction by donating protons to oxygen. Proton migration and oxygen dissociation are found to happen concertedly.

The tridiagonal J-matrix approach has been used to calculate the low and moderately high-lying eigenvalues of the rotating shifted Tietz–Hua (RSTH) oscillator potential. The radial Schrödinger equation is solved efficiently by means of the diagonalization of the full Hamiltonian matrix, with the Laguerre or oscillator basis. Ro–vibrational bound state energies for 11 diatomic systems, namely
,
,
, NO, CO,
,
,
,
,
, and NO^{+}, are calculated with high accuracy. Some of the energy states for molecules are reported here for the first time. The results of the last four molecules have been introduced for the first time using the oscillator basis. Higher accuracy is achieved by calculating the energy corresponding to the poles of the S-matrix in the complex energy plane using the J-matrix method. Furthermore, the bound states and the resonance energies for the newly proposed inverted Tietz–Hua IRSTH-potential are calculated for the H_{2}-molecule with scaled depth. A detailed analysis of variation of eigenvalues with *n,*
quantum numbers is made. Results are compared with literature data, wherever possible. © 2015 Wiley Periodicals, Inc.

The tridiagonal J-matrix method has been successfully used for a number of situations of physical and chemical interest. Here that J-matrix method is used to calculate the Ro–vibrational eigenvalues of the Tietz–Hua (TH) potential for 11 diatomic systems, four of which are reported for the first time. The bound and resonance eigenvalues for the newly proposed inverted TH potential are calculated for the H_{2}-molecule, with scaled depth, and compared with the inverted Morse potential.

This Special Issue focuses on recent advances in density functional theory. Though 50 years have passed since the formulation of Kohn-Sham density functional theory, many open questions remain. Some of the topics in this Special Issue include open mathematical questions, the development of more accurate density functionals, the development of accurate kinetic energy functionals, and applying density functional theory to solve new and exciting scientific problems. The Special Issue features the highlights of the 16th International Conference on Density Functional Theory and its Applications held in Debrecen, Hungary, August 31 – September 4, 2015.

A few problems in DFT are posed that have mathematical flavors. Is there a coordinate scaling equality for the correlation energy with an arbitrary density? Is it possible to obtain the exact ground-state energy from the exact ground-state density, or does the presence of certain functionals with zero functional derivatives prevent this? How common are non-v-representable densities? © 2016 Wiley Periodicals, Inc.

There are a number of mathematical problems in density functional theory for which solutions have not yet been found. Is there a coordinate scaling equality for the correlation energy with an arbitrary density? Is it possible to obtain the exact ground-state energy from the exact ground-state density, or does the presence of certain functionals with zero functional derivatives prevent this? How common are non-v-representable densities?

Hartree-Fock (HF) theory makes the prediction that for neutral atoms the chemical potential (*μ*) is equal to minus the ionization potential (*I*). This has led us to inquire whether this intimate relation is sensitive to electron correlation. We present here therefore some discussion of the predictions for neutral atoms and atomic ions, and some homonuclear diatomic molecules. An account of fairly recent progress in obtaining the HF ionization potentials for the isoelectronic series of He, Be, Ne, Mg, and Ar-like atomic ions is first considered. The
expansion for total non-relativistic energy of atomic ions evokes that
is not very sensitive to the introduction of electron correlation. The connection between *μ* and *I* for neutral atoms via the Pauli potential (*V*_{P}) is then examined. We focus on the relation of *V*_{P} to more recent advances in density functional theory (DFT) plus low-order density matrix theory. In this context, the example of nonrelativistic Be-like atomic ions is treated. Afterward, we introduce the bosonized equation for the density amplitude
, which emphasizes the major role that plays
in DFT. For spherical atomic densities, the bosonized potential argument strongly suggests also that
remains valid in the presence of electron correlation. Finally, numerical estimates of *μ* and *I* from natural orbital functional (NOF) theory are presented for neutral atoms ranging from H to Kr. The predicted vertical *I* by means of the extended Koopmans' theorem are in good agreement with the corresponding experimental data. However, the NOF theory of *μ* lowers the experimental values considerably as we approach to noble gas atoms though oscillatory behavior is in evidence. © 2015 Wiley Periodicals, Inc.

The prediction that the chemical potential (μ) is equal to minus the ionization potential (*I*) has been investigated. This connection via the Pauli potential is examined. Recent progress in DFT evokes that μ = −*I* is not very sensitive to the electron correlation. Estimates from NOF theory are presented for atoms ranging from H to Kr. The predicted *I* are in good agreement with the experiment. However, values of μ lowers considerably for noble-gas atoms though oscillatory behavior is in evidence.

Machine learning (ML) is an increasingly popular statistical tool for analyzing either measured or calculated data sets. Here, we explore its application to a well-defined physics problem, investigating issues of how the underlying physics is handled by ML, and how self-consistent solutions can be found by limiting the domain in which ML is applied. The particular problem is how to find accurate approximate density functionals for the kinetic energy (KE) of noninteracting electrons. Kernel ridge regression is used to approximate the KE of non-interacting fermions in a one dimensional box as a functional of their density. The properties of different kernels and methods of cross-validation are explored, reproducing the physics faithfully in some cases, but not others. We also address how self-consistency can be achieved with information on only a limited electronic density domain. Accurate constrained optimal densities are found via a modified Euler-Lagrange constrained minimization of the machine-learned total energy, despite the poor quality of its functional derivative. A projected gradient descent algorithm is derived using local principal component analysis. Additionally, a sparse grid representation of the density can be used without degrading the performance of the methods. The implications for machine-learned density functional approximations are discussed. © 2015 Wiley Periodicals, Inc.

Machine learning has been used to find accurate approximate density functionals. In this approach, kernel ridge regression is used to approximate the kinetic energy of noninteracting fermions in a one dimensional box as a functional of their density. Key procedures in this method including the choice of kernel, different cross-validation, representation of sparse grid, manifold reconstruction and projected gradient descent algorithm are explored and documented.

The fundamental requirements for a computationally tractable Density Functional Theory-based method for relativistic *f*- and (nonrelativistic) *d*-electron materials and compounds are presented. The need for basing the Kohn–Sham equations on the Dirac equation is discussed. The full Dirac scheme needs exchange-correlation functionals in terms of four-currents, but ordinary functionals, using charge density and spin-magnetization, can be used in an approximate Dirac treatment. The construction of a functional that includes the additional confinement physics needed for these materials is illustrated using the subsystem-functional scheme. If future studies show that a full Dirac, four-current based, exchange-correlation functional is needed, the subsystem functional scheme is one of the few schemes that can still be used for constructing functional approximations. © 2016 Wiley Periodicals, Inc.

Density Functional Theory (DFT) is a reformulation of the fundamental Dirac/Schrödinger Equation, allowing for computationally tractable quantum mechanical calculations. The method is extensively used in material science and its accuracy is set by the approximation for the exchange-correlation energy functional, *E*_{xc}. Accurate functionals are available for many types of materials and this article reviews the methods development needed to extend the accurate use of the method to *d*- and *f*-electron materials and compounds.

We discuss six questions related to the recent “strongly constrained and appropriately normed” (SCAN) meta-generalized gradient approximation (meta-GGA): (1) When and why should a semilocal approximation to the density functional for the exchange-correlation energy be accurate? (2) What is the right dimensionless ingredient for a meta-GGA, and why? (3) In the construction of density functional approximations, should we satisfy more or fewer exact constraints? (4) Is there a tight lower bound on the exchange energy for all spin-unpolarized densities? (5) Should a semilocal approx- imation yield any intermediate-range van der Waals interaction? (6) Do semilocal functionals make consistent predictions for the energy differences between different molecules (and thus presumably for reaction and formation energies)? © 2016 Wiley Periodicals, Inc.

The strongly constrained and appropriately normed (SCAN) meta-GGA may be a major step in the nonempirical or constraint-based construction of the approximation to the density functional for the exchange-correlation energy. SCAN satisfies all 17 known exact constraints appropriate to a semilocal functional, plus appropriate norms, by employing the orbital kinetic energy density as well as the electron density and its gradient. Six questions related to such functionals are addressed here.

Alternatives to the Ornstein–Zernike direct correlation function (DCF) are proposed, parameterized to reproduce the homogeneous electron liquid, and applied to atomic and molecular systems. This generalizes the work of Amovilli and March [*Phys. Rev. B* **76**, 195104 (2007)], where the ordinary Ornstein–Zernike DCF was used. Unlike the Ornstein–Zernike DCF, one of the alternative DCFs explored in this present work produces normalized exchange-correlation holes. © 2016 Wiley Periodicals, Inc.

Alternatives to the Ornstein–Zernike direction correlation function (DCF) are proposed, parametrized to reproduce the homogeneous electron liquid, and subsequently applied to atomic and molecular systems. One of the alternative DCFs explored in this present work is consistent with normalized exchange-correlation holes.

Euler equations for a family of descriptors of the spherically symmetric Coulomb systems are derived and discussed. Generalized Weizsäcker and Pauli energies and potentials are introduced. © 2016 Wiley Periodicals, Inc.

The most popular application of density functional theory is done within the Kohn–Sham scheme, though in principle orbital-free calculations are also possible. Because of the lack of accurate approximation for the kinetic energy functional, orbit-free calculations are not reliable. Recently, an approach has been proposed to solve the orbital-free problem for spherically symmetric systems. This approach is now generalized to derive Euler equations for a family of descriptors of Coulomb systems.

The importance of the semi-core-valence interaction for plane-wave pseudopotential calculations with exact exchange is investigated for group IVA, IIIA–VA, and IIB–VIA semiconductors. Results for different valence spaces, either omitting or including the semi-core d- and/or the semi-core sp-states, are compared with full-potential LAPW all-electron data. It is found that for group IIB, IIIA, and IVA elements only the valence space including all semi-core states leads to accurate band structures. In fact, no real improvement over the minimum valence space is obtained for group IIIA and IVA elements, if only the semi-core d-states are taken into account. The particular relevance of the semi-core sp-states arises from the nonlocality of the exact exchange, which makes the exchange potential in the valence region sensitive to orbital structures located in the semi-core region (such as the nodes of the valence states). In contrast, even the valence space without any semi-core states yields very accurate results in the case of group VA elements, indicating the onset of the decoupling of the M-shell from the valence states. To deal with valence spaces including all semi-core states a proper construction of pseudopotentials is essential. While usually the energetically lowest state in the valence space is utilized to generate the pseudopotential for the corresponding angular momentum, it is shown here that this procedure can induce significant errors, when applied in the presence of semi-core states. Accurate results are only obtained, if the pseudopotentials are generated from the (occupied) valence states (under the constraint that the corresponding pseudoorbitals have one node), the reason being that the norm-conservation of the valence states is more important for the electronic structure of the bulk than that of the semi-core states. As a byproduct, it is shown that highly accurate pseudopotential results can also be obtained for solid Ne. © 2016 Wiley Periodicals, Inc.

The Kohn–Sham band gaps of fourth and fifth row group IVA, IIIA–VA, and IIB–VIA semiconductors obtained with exact exchange density functional calculations show a substantial variation: pseudopotential (PP) results differ from each other and from all-electron data beyond the accepted error of the PP approach. In this article it is shown that only PP valence spaces including the complete semi-core shell lead to accurate band structures for group IIB, IIIA, and IVA elements and why inclusion of only the d-states is not sufficient.

Ensemble density functional theory (DFT) is a theory potentially able to describe electronic states inaccessible to traditional time-dependent DFT approaches, e.g. Rydberg and double excitations. When combined with ensemble wavefunction approaches through a range-separation scheme of Stoll and Savin (Density Functional Methods in Physics, 1985, 177-207), a resulting multiconfiguration ensemble DFT is able to address also such challenging phenomena as bond breaking in the electronically excited molecules. Ensemble DFT is, however, crippled by the so-called “ghost interaction” error, analogous to the self-interaction error in the ground-state DFT. We are exploring ways to alleviate this effect. We also study the importance of spin polarization in the density functional, the self-consistency effects and the impact of tunable parameters on the quality of shapes of potential energy surfaces. © 2016 Wiley Periodicals, Inc.

Ensemble density functional theory (DFT) is a theory potentially able to describe electronic states inaccessible to traditional time-dependent DFT approaches, e.g. Rydberg and double excitations. When combined with ensemble wavefunction approaches, a resulting multiconfiguration ensemble DFT is also able to address such challenging phenomena as bond breaking in the electronically excited molecules. “Ghost interaction” error, analogous to the self-interaction error in the ground-state DFT, limits ensemble DFT's general use and needs to be alleviated.