The mechanism of ionization of an H atom interacting with intense laser electric fields is altered when a strong, oscillating magnetic field is applied along a direction parallel to the laser field. In this first study, these two strongly nonperturbative situations have been combined together and the corresponding time-dependent (TD) Schrödinger equation has been numerically solved without using any basis set. The electric field arising out of the magnetic field and the magnetic field arising out of the laser electric field are found to be negligibly small, thereby not affecting the results. There are two main, apparently counter-intuitive results from this study of parallel fields of the same frequency but different field strengths: (1) In presence of an oscillating magnetic field, the ionization rate due to the laser field diminishes, and (2) increasing the laser intensity, keeping the magnetic field strength the same, makes the electron density ionize with a lesser rate, in contrast to the situation with intense lasers in the absence of a strong TD magnetic field. © 2015 Wiley Periodicals, Inc.

The strong oscillating magnetic field localizes the electron density more around the nucleus of H atom. The laser electric field, when in phase with the magnetic field, sweeps the electron density more toward nucleus. As a result, the ionization decreases with increasing laser intensity.

Graphene is an exciting material for optoelectronics and plasmonics. Its optical response may be changed under mechanical action, such as stretching or corrugation, and with confinement of a size in a certain direction. Theoretical investigations play an important role in interpretation of experimental data and stimulating a search for novel graphene architectures. Thereby, it is important to analyze restrictions of modern approaches in calculation of optical properties of graphene-based objects and, particularly, to reveal an impact of electron–electron and electron–hole interactions on the position and shape of optical features. Here, we review the recent progress in quantum-chemical calculations of monolayer and few-layer graphenes, graphene ripples, and dots in a light of optical excitations. © 2015 Wiley Periodicals, Inc.

Many-body interactions may markedly modify the optical transitions in graphene-based structures. This review analyses the changes in the excitonic binding energy depending on deformation or size-confinement of graphene lattice and interlayer coupling. The theoretical results are compared with optical absorption and low-loss EEL spectra.

Semiclassical simulations of spectrum and dynamics of complex molecules require statistical sampling of coordinates and momenta. The effects of using thermal and quantum samplings are analyzed taking pyrrole as a test case. It is shown that there are significant differences in the results obtained with each of these two approaches. Overall, quantum sampling based on a Wigner distribution renders superior results, comparing well to the experiments. Dynamics simulations based on surface hopping and ADC(2) reveal that pyrrole internal conversion to the ground state occurs not only through H-elimination path, but also through ring-distortion paths, which have been systematically neglected by diverse experimental setups. The analysis of the reaction paths also shows that the ionization potential varies by more than 5 eV between ionization of the excited state at the Franck–Condon region and at the intersections with the ground state. This feature may have major implications for time-resolved photoelectron spectroscopy. © 2015 Wiley Periodicals, Inc.

Semiclassical simulations of spectrum and dynamics of complex molecules require statistical sampling of coordinates and momenta. The effects of using thermal and quantum samplings to create initial conditions for dynamics and spectrum simulations are analyzed for pyrrole as test case. There are significant differences in the results obtained with each of these two approaches. Overall, quantum sampling based on a Wigner distribution renders superior results compared to the experiments.

The origin of singlet–triplet energy difference, Δ*E*_{ST}, in π-conjugated molecules was elucidated by carrying out *ab initio* calculations of acene molecules at scaled opposite-spin (SOS)-CIS(D_{0}) level of theory using aug-cc-pVDZ basis sets. Both singlet and triplet excitation energies decrease monotonously as π-conjugation expands. However, Δ*E*_{ST} is found to evolve in rather complicated manner; it increases in going from benzene to anthracene and diminishes thereafter. To better understand this behavior, excitation energy decomposition at CIS level of theory was conducted, and the variations of Coulomb- and exchange-type integrals between the excited and remnant electrons as a function of π-conjugation length were discussed. The effects of dynamic electron correlation on both singlet and triplet excitation energies and Δ*E*_{ST} were also discussed. © 2015 Wiley Periodicals, Inc.

Thermally activated delayed fluorescence (TADF) phenomenon provides a viable way to replace expensive heavy-metal containing phosphors with cheap organic luminophores for OLED applications. One of the key parameters for the efficacy of such interconversions is the singlet-triplet energy difference, ΔE_{ST}. Quantum chemical calculations provide better understanding of this phenomenon and explain the difference in the nature of singlet and triplet excited states and the origin of ΔE_{ST} via excitation energy decomposition.

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.

Due to ligand non-innocence and reversible one-electron-transfer processes dithiolene complexes have been intensively studied both experimentally and computationally. While the substitution of the ligating sulfur atoms by selenium provides a means to delicately tune the behavior of dithiolene compounds, diselenolene complexes have not been as thoroughly examined. Yet, the search for such ligands has been ongoing since the 1970s. Thus, we have looked at several metal-bisdiselenolene complexes and have compared key properties of these complexes with their bisdithiolene analogues to determine the effect of substituting the chalcogen atom. The results herein show that substitution of the sulfur atoms by selenium within these complexes only subtly changes the thermodynamics and kinetic reactivity of bisdithiolene complexes while not significantly affecting the geometries of the complexes. The significance being that the relatively minor structural changes that occur upon redox is a key feature of dithiolene complexes. Due to ligand non-innocence and reversible one-electron-transfer processes dithiolene complexes have been intensively studied, however, diselenolene complexes have not. First-principles calculations show that substitution of the sulfur atoms by selenium within the investigated complexes does offer the ability to subtly tune the thermodynamics and kinetic reactivity of bisdithiolene complexes, while not significantly affecting the geometries of the complexes. © 2015 Wiley Periodicals, Inc.

Due to ligand non-innocence and reversible one-electron-transfer processes, dithiolene complexes have been intensively studied; however, diselenolene complexes have not. First-principles calculations show that substitution of the sulfur atoms by selenium within the investigated complexes does offer the ability to subtly tune the thermodynamics and kinetic reactivity of bisdithiolene complexes, while not significantly affecting the geometries of the complexes.

State-of-the-art in the area of quantum-chemical modeling of electron transfer (ET) processes at metal electrode/electrolyte solution interfaces is reviewed. Emphasis is put on key quantities which control the ET rate (activation energy, transmission coefficient, and work terms). Orbital overlap effect in electrocatalysis is thoroughly discussed. The advantages and drawbacks of cluster and periodical slab models for a metal electrode when describing redox processes are analyzed as well. It is stressed that reliable quantitative estimations of the rate constants of interfacial charge transfer reactions are hardly possible, while predictions of qualitatively interesting effects are more valuable. © 2015 Wiley Periodicals, Inc.

Electron transfer reactions play an exceedingly important role in our life. Such chemical reactions occurring at multifarious electrochemical interfaces can be regarded as the most complicated. To understand some exciting features of redox processes observed in experiment, as well as to control electron transfer in a proper way, one needs a molecular level insight into the elementary act. This can be attained in the framework of a rigorous quantum mechanical theory combined with the power of modern computational chemistry. In this article we discuss the most interesting model approaches which are bridging theoretical predictions with experiment. For quantum chemistry, on the other hand, the realm of various redox reactions remains tour de force and prompts the further development of computational methods.

Many important properties of crystals are the result of the local defects. However, when one address directly the problem of a crystal with a local defect one must consider a very large system despite the fact that only a small part of it is really essential. This part is responsible for the properties one is interested in. By extracting this part from the crystal one obtains a so-called cluster. At the same time, properties of a single cluster can deviate significantly from properties of the same cluster embedded in crystal. In many cases, a single cluster can even be unstable. To bring the state of the extracted cluster to that of the cluster in the crystal one must apply a so-called embedding potential to the cluster. This article discusses a case study of embedding for ion-covalent crystals. In the case considered, the embedding potential has two qualitatively different components, a long-range (Coulomb), and a short-range. Different methods should be used to generate different components. A number of approximations are used in the method of generating an embedding potential. Most of these approximations are imposed to make the equations and their derivation simple and these approximations can be easily lifted. Besides, the one-determinant approximation for the wave function is used. This is a reasonably good approximation for ion-covalent systems with closed shells, which simplifies the problem considerably and makes it tractable. All employed approximations are explicitly stated and discussed. Every component of generation methods is described in details. The proofs of used statements are provided in a relevant appendix. © 2015 Wiley Periodicals, Inc.

An immediate solution of the Schroedinger equation for a real crystal is impossible due to an enormous number of particles in the system and a complicated system structure. However, in the presence of local defects such as impurity atom or the electron localized in anion vacancy, their properties are determined by a comparatively small region of the crystal. While this small region can be modeled explicitly, embedding potentials provide an effective way to incorporate it into the crystal.

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.

The equilibrium geometries, relative stabilities, electronic and magnetic properties of small Rh_{n}Ca (*n* = 1–9) clusters have been investigated by DFT calculations. The obtained results show that the three-dimensional geometries are adopted for the lowest-energy Rh_{n}Ca clusters, and the doped Ca atom prefers locating on the surface of the cluster. Based on the analysis of the second-order difference of energies, fragmentation energies and the HOMO-LUMO energy gaps, we identify that the Rh_{4}Ca, Rh_{6}Ca, and Rh_{8}Ca clusters are relatively more stable than their neighboring clusters, and the doping of Ca enhances the chemical reactivity of the pure Rh_{n} clusters, suggesting that the Rh_{n}Ca clusters can be used as nanocatalysts in many catalytic reactions. The magnetic moment for these clusters is mostly localized on the Rh atoms, and the doping Ca atom has no effect on the total magnetic moment of Rh_{n}Ca clusters. The partial density of states, VIP, VEA, and *η* of these clusters in their ground-state structures were also calculated and discussed. © 2015 Wiley Periodicals, Inc.

Small rhodium clusters find *many* applications in several *fields* such as electronics, magnetism, catalysis and nanotechnology. Therefore, in this work, the geometries, stabilities, electronic, and magnetic properties of small Ca-doped Rh clusters will be studied by means of density functional theory (DFT). It is hoped that the obtained results of our study would be informative to understand the influence of cluster size on its properties and could provide a guideline for future experiments.

Vibronic theory of heteroligand systems is applied to deal with the model pseudospin Hamiltonian (PSH) that describes structural phase transitions of the KDP-family ferroelectrics. In this approach, the PSH consists of three terms, describing proton–proton interactions, the potential energy of lattice oscillators, and the interaction between these two subsystems. The Ising form for the configuration energies of the Bethe cluster method (where the PSH's parameters depend explicitly on electronic structure and on vibronic constants of the AO_{4}-containing structural units) remains valid up to the second order of perturbation theory. The Ising theory with the PSH parameters calculated by means of quantum chemical methods is applied further to obtain the estimates of thermodynamic characteristics, in particular, the critical temperature *T*_{c} of the structural phase transition. © 2015 Wiley Periodicals, Inc.

The quantum-chemical scheme of the microscopic description for structural phase transitions in H-bonded ferroelectrics and related materials, based on vibronic theory of heteroligand systems and ab initio calculated parameters of the pseudospin Hamiltonian, allows to estimate the critical temperature T_{c} of the structural phase transition and its dependence on tunneling.

The initial molecular structure of 2,2′-bis(4-trifluoromethylphenyl)- 5,5′-bithiazole has been optimized in the ground state using density functional theory (DFT). The distribution patterns of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) have also been evaluated. To shed light on the charge transfer properties, we have calculated the reorganization energy of electron *λ*_{e}, the reorganization energy of hole *λ*_{h}, adiabatic electron affinity (EA_{a}), vertical electron affinity (EA_{v}), adiabatic ionization potential (IP_{a}), and vertical ionization potential (IP_{v}) using DFT. Based on the evaluation of hole reorganization energy, *λ*_{h}, and electron reorganization energy, *λ*_{e}, it has been predicted that 2,2′-bis(4-trifluoromethylphenyl)-5,5′-bithiazole would be a better electron transport material. Finally, the effect of electric field on the HOMO, LUMO, and HOMO–LUMO gap were observed to check its suitability for the use as a conducting channel in organic field-effect transistors. © 2015 Wiley Periodicals, Inc.

Unlike conventional electronics, organic electronic materials are designed from carbon-based small molecules or polymers. The most advantageous benefits of organic materials are their low cost and weight as well as their more environmentally friendly nature. The molecular structure and properties of the large organic molecule 2,2′-bis(4-trifluoromethylphenyl)-5,5′-bithiazole are evaluated by means of first-principles calculations to test its possible applications in organic electronics.

High energy irradiation to the hydrogen bonded system is important in relevance with the initial process of DNA and enzyme damages. In the present study, the effects of radiation to catalytic triad have been investigated by means of direct *ab-initio* molecular dynamics (AIMD) calculation. As a model of the catalytic triad, Ser-His-Glu residue, which is one of the important enzymes in the acylation reaction, was examined. The ionization and electron attachment processes in Ser-His-Glu were investigated as the radiation effects. The direct AIMD calculation showed that a proton of His is spontaneously transferred to carbonyl oxygen of Glu after the ionization. However, the whole structure of catalytic triad was essentially kept after the ionization. On the other hand, in the case of the electron capture in the model catalytic triad Ser-His-Glu, the dissociation of Glu residue from [Ser-His]^{−} was found as a product channel. The mechanism of ionization and electron capture process in the catalytic triad was discussed on the basis of theoretical results. © 2015 Wiley Periodicals, Inc.

The effects of high energy irradiation to hydrogen bonded systems play an important role in DNA and enzyme damages. We investigated hole and electron capture processes of a model of the catalytic triad, Ser-His-Glu residue, by means of direct ab-initio molecular dynamics (AIMD) calculation. The fast proton transfer was found in the hole capture in the catalytic triad.

Diamondoids are hydrocarbons having a carbon scaffold comprised from polymer-like composites of adamantane cages. This article describes computed total energies and “SWB-tension” energies (often referred to as “strain” energies) for species having *n* adamantane or diamantane units sharing pairwise: one carbon atom (spiro-[*n*]adamantane or spiro-[*n*]diamantane); one CC bond (one-bond-sharing-[*n*]adamantane or one-bond-sharing-[*n*]diamantane); or one chair-shaped hexagon of carbon atoms (1234-helical-cata-[*n*]diamantanes). Each of the five investigated polymer-like types is considered either as an acyclic or a cyclic chain of adamantane- or diamantane-unit cages. With increasing *n* values, SWB-tension energies for acyclic aggregates are found to increase linearly, while the net SWB-tension energies of cyclic aggregates often go thru a minimum at a suitable value of
. In all five cases, a limiting common energy per unit (
) is found to be approached by both cyclic and acyclic chains as
, as revealed from plots of
versus 1/*n* for acyclic chains and of
versus 1/*n*^{2} for cyclic chains. © 2015 Wiley Periodicals, Inc.

Total energies and strain energies calculated with PM6 and MM2 programs, respectively, are presented for cyclic and acyclic chains formed by *n* adamantane or diamantane units sharing with an adjacent unit one vertex, one CC bond, or one 6-membered ring. *Dualists* consist in virtual vertices at centers of adamantane units, and of edges connecting vertices in adjacent rings sharing hexagons. Color codes: olive for virtual vertices of dualists (upper figure); red, black, and blue for quaternary (C), tertiary (CH), and secondary carbon atoms (CH_{2}), respectively. Strain energies per unit depend linearly on 1/*n*^{2} for cyclic chains (middle figure) with adamantane units sharing hexagons), and on 1/*n* for acyclic chains (lower figures). With increasing *n* values, strain energies converge to a common value for cyclic and acyclic chains.

Recently, multi-parameter potential has been introduced and had been discussed as special cases of other potential model, that is why we are interested to the study of such a potential. In order to study this potential, the *D*-dimensional Schrödinger has been presented in detail and the scattering state with any arbitrary *J*-state due to this potential has been investigated approximately. After this step, we have discussed analytically the scattering and bound state for some special cases in *D*-dimensional situations which play important roles in physics. © 2015 Wiley Periodicals, Inc.

The scattering state solutions of the Schrodinger equation with solvable multiparameter exponential type potentials with improved approximation scheme for the centrifugal term are investigated in this work, with the aim to obtain the normalized wave functions as expressed in terms of the hypergeometric functions of the scattering state. The formula for the scattering phase shift is consequently derived.

The coordination and energetics of low-lying structures of [Li(EC)* _{n}*]

The local coordination environment of Lithium ions in ethylene carbonate (EC) solvent is still under debate despite being the subject of several experimental and theoretical works. Density Functional Theory calculations are employed to elucidate the coordination chemistry of the lithium ion in EC using [Li(EC)_{n}]+ (n=1–7) clusters and polarizable continuum methods as model for the solution.

The effect of the stacked azo-chromophore dimer formation on the values of static first hyperpolarizability is studied in the framework of the DFT-based approach; calculations were also performed at the MP2 level. A number of dispersion-corrected density functionals—В97D, ωВ97X-D, and M06-2X—is tested to calculate the structure of the dimer, the value of binding energy, and molecular nonlinear optical characteristics. According to the QTAIM analysis, the presence of bond critical points is revealed in the intermolecular region, the signs and values of topological characteristics giving evidence for the noncovalent van der Waals interaction between the chromophores. The formation of stacks results in moderate increase of dimer static first hyperpolarizability as compared to that of a single chromophore, the effect depending on the relative shift of the chromophores in dimer. In a special case of greatly shifted chromophores, this enhancement of the first hyperpolarizability becomes appreciable and achieves 72%. © 2015 Wiley Periodicals, Inc.

Formation of dimers from azochromophores, essentially shifted with regard to each other, results in the appreciable enhancement of first hyperpolarizability *β* (up to 72%) as compared to that of a single chromophore. Chromophores in dimer are shown to be bound by van der Waals interactions. Reliable values of *β* of stacked dimer are provided in the framework of DFT with dispersion corrections being taken into account, in particular, with range-separated ωB97X-D functional.

Theoretical methods involving molecular dynamics (MD) simulation and density functional theory were performed to investigate the different molecular ratios, mechanical Properties, structure, trigger bond, and intermolecular interaction of hexaazaisowurtzitane (CL-20)/nitroguanidine (NQ) cocrystal explosive. Results of MD simulation show that CL-20 and NQ packed in ratios of 1:1 present the larger binding energy and better mechanical properties than any other molecular ratios, which indicates 1:1 cocrystal can form the stable crystal structure. Shorter length and larger dissociation energy of trigger bond in composite structure than in isolated CL-20 component suggests that the cocrystal may exhibit less sensitive than CL-20. Analyses of atoms in molecules, reduced density gradient, and natural bond orbital confirm that intermolecular interactions are mainly derived from a series of weak hydrogen bond and strong vdW forces, involving of NH···O, CH···O, CH···N, O···N, and O···O. Additionally, composite structures of **2** and **3** bringing us more attractive performance will act as a key role in constructing of CL-20/NQ cocrystal explosive. © 2015 Wiley Periodicals, Inc.

CL-20 is powerful energetic material with good detonation performance, but high sensitivity limits its widespread implementation. Nitroguanidine (NQ) is proposed as a cocrystal to limit the sensitivity of CL-20. Molecular Dynamics simulations and Density Functional Theory are used to optimize the molecular ratio and intermolecular interaction nature of the CL-20/NQ cocrystal explosive. By increasing the strength of trigger bonds van der Waals forces reduce the sensitivity of the cocrystal explosive.

Using a linearized augmented cylindrical wave (LACW) approach taking into account the screw and rotational symmetries of carbon nanotubes (CNTs), the first principles technique for the spin-dependent band structure calculations of single-walled CNTs is developed. The method is applicable to any tubule independent on diameter and chirality. The calculations are based on the two-component relativistic Hamiltonian and muffin-tin and exchange approximations for potentials. As example, the band structures of the three chiral, one armchair, and one zigzag CNTs are calculated and presented as the functions of the screw wave vector and rotational quantum number. The spin-orbit coupling effects appear as splitting of some nonrelativistic electron bands equal to between the 0.01 and 1 meV depending on the CNTs structure, rotational quantum number, and Brillouin zone position. In agreement with previous empirical tight-binding theories, almost perfect polarization of spin is observed in the case of chiral tubules. © 2015 Wiley Periodicals, Inc.

Single-walled carbon nanotubes have a helical tubular atomic structure. In the relativistic cylindrical wave method, such symmetry and structural features of CNTs are taken into account explicitly allowing researchers to perform first-principles calculations of the spin-dependent band structure of any tubules. Spin-orbit gaps up to 1 meV and spin polarization effects are quantitatively predicted for several achiral and chiral nanotubes using this approach.

We review the basics of the Effective Hamiltonian Crystal Field (EHCF) method originally targeted for calculations of the intra-shell excitations in the d-shells of coordination compounds of the first row transition metal. The formalism employs in the concerted way the McWeeny's group-function approximation and the Lowdin partition technique. It is needed for description of the transition metal complexes with partially filled d-shells where the (static) electronic correlations are manifested. These features are particularly important for electron fillings close to “half shell” ones occurring, for example, in the Fe^{2+} and Fe^{3+} ions. Recently we extended this methodology to polynuclear coordination compounds to describe magnetic interactions of the effective spins residing in several open d-shells. This improves the accuracy from about 1000 cm^{−1} to that of about 100 cm^{−1}, that is, eventually by an order of magnitude. This approach implemented in the MagAixTic package is applied here to a series of binuclear Fe(III) complexes featuring μ-oxygen superexchange pathways. The results of calculations are in a reasonable agreement with available experimental data and other theoretical studies of protonated bridges. Further we discuss the application of the EHCF to analysis of Mosbauer experiments performed on two organometallic solids: FeNCN and Fe(HNCN)_{2} and conjecture a new thermal effect in the latter material. © 2015 Wiley Periodicals, Inc.

Ideally, a molecule or a solid should be calculated/modeled using a single numerical method. However, the physical conditions in different parts of a complex molecule may be fairly different, thus requiring different approximations to describe them. The Effective Hamiltonian Crystal Field method is one of the earliest attempts of implementing this idea. This approach singles out the d-shells of transition metal complexes and represents an efficient and physically transparent tool for modeling them.

A short review of the recent studies aimed at the search for novel stable polyhedral structures engineered by superstruction of the classical parent highly strained but kinetically stable organic predecessors, tetrahedrane, cubane, and dodecahedrane is presented. A series of stable structures B_{80}H_{20}, C_{80}H_{20}, and Al_{80}H_{20} with tetrahedral B_{4}H, C_{4}H, and Al_{4}H fragments displacing CH vertices of the cubane and dodecahedron scaffolds was computationally designed. In the similar way, the molecules С_{104}H_{32}, В_{104}H_{32}, В_{64}С_{40}H_{32} and В_{40}С_{64}H_{32}, Al_{104}H_{32}, Si_{104}H_{32} and Al_{64}Si_{40}H_{32} representing the supermolecular models of the corresponding crystal structures were constructed on the basis of the diamond crystal lattice in which carbon atoms are replaced by B_{4}, C_{4}, and Al_{4} and Si_{4} tetrahedral moieties, respectively. The effect of crystalline packing exerted on the conformation of the non-rigid molecular structures is discussed by an example of supermolecular modeling of the structural configuration of a ten molecule sampling of a bis-chelate Ni(II) complex. © 2015 Wiley Periodicals, Inc.

Simulations play an important role in the search for novel stable polyhedral structures, engineered on the base of the supertetrahedral systems. A series of stable boranes, carbons, aluminiums, and silicons structures is computationally designed on the basis of the diamond crystal lattice in which carbon atoms are replaced by corresponding tetrahedral moieties. The effect of crystalline packing on the conformation of the non-rigid molecular structures is also discussed.

Using density functional theory (DFT) in conjunction with ultraviolet (UPS) and X-ray photoelectron spectroscopy (XPS), we investigated a number of complexes and macromolecules. We have shown on a large set of UPS, XPS, and DFT data that the calculated Kohn–Sham energies of organic and metalorganic complexes can be used as approximate ionization energies (IEs). It is possible to evaluate IEs with an accuracy of 0.1 eV with the density functional approximation (DFA) defect approach. This method has been successfully tested on a large number of boron β-diketonates and d-metal chelate and sandwich complexes. We interpreted the bands in the valence region of the XP spectra of macromolecular organosilicon compounds in the solid state by taking into account the density of states and the ionization cross-sections. According to DFT calculation results, the one-electron states in the valence region of the model compounds correlate with the positions of the spectral band maxima. © 2015 Wiley Periodicals, Inc.

Calculated molecular orbital (MO) energies agree with experimental ionization energies (with an accuracy of up to 0.1 eV based on density functional theory calculations) by applying a coefficient. This depends on the MO composition and can be transferred to wide range of compounds.

The exact basic equation of motion for the microscopic density of system of interacting particles is derived. In this derivation, no probabilistic hypotheses or assumptions are used. This integro-differential equation is the equation of motion of nonlinear classical scalar field with respect to the microscopic density. The possible mechanisms of transition of many-particle system in equilibrium state are discussed. On the basic equation, the exact integral equation for the equilibrium spatial distribution of the particles is obtained. It is shown that the Boltzmann distribution and the Vlasov equation are special cases of this integral equation. The wave equation for almost homogeneous systems with interparticle interactions is obtained. Effect of interparticle interactions on the dispersion law of sound is established. © 2015 Wiley Periodicals, Inc.

The exact basic equation of motion for the microscopic density of system of interacting particles is derived. In this derivation, no probabilistic hypotheses or assumptions are used. This integro-differential equation is the equation of motion of nonlinear classical scalar field with respect to the microscopic density. The possible mechanisms of transition of many-particle system in equilibrium state are discussed. On the basic equation, the exact integral equation for the equilibrium spatial distribution of the particles is obtained. It is shown that the Boltzmann distribution and the Vlasov equation are special cases of this integral equation. The wave equation for almost homogeneous systems with interparticle interactions is obtained. Effect of interparticle interactions on the dispersion law of sound is established.

In this review paper, the main ideas and results of application of the linearized augmented cylindrical wave (LACW) method for the electron properties of the single-walled, double-walled, embedded, and intercalated nanotubes are summarized. We start with the simplest case of the achiral single-walled (*n*, 0) and (*n*, *n*) tubules having small translational unit cells. Then, the electron properties of chiral (*n*, *m*) nanotubes having very large translational cells are discussed with account of tubules possessing rotational and screw symmetries. Based on the LACW and Green's function techniques, the *ab initio* numerical approach to calculating the electron local densities of states of the substitutional impurities in the nanotubes is presented. The relativistic version of LACW theory is described and applied to calculating the effects of spin–orbit coupling on π-bands of the cumulenic (C)* _{n}* and polyynic (C

Nanotubes are multiatomic systems with perfect cylindrical geometry. In the construction of the linearized augmented cylindrical waves method for the calculation of the electronic properties of nanotubes, their cylindrical structure needs to be taken explicitly into account. This allows the modeling of a variety of nanotubes: achiral and chiral, single-walled and double-walled, embedded and intercalated. The relativistic effects are also taken into account in the described cylindrical wave method.

The review proposed summarizes the results of investigations on the adiabatic potential energy surfaces (PESes) for the radical ions of some derivatives of highly symmetric organic molecules such as benzene and cyclohexane. The results obtained show that the main feature of the PESes of highly symmetric Jahn–Teller ions, namely conical intersection, may persist for their low-symmetric derivatives. Hence, their PESes have a pseudorotational shape resulting from the intersection avoidance. A distinctive feature of radical anions of fluorine containing aromatic compounds is the planar structure disturbance due to the vibronic coupling of the ground π and low-lying excited σ states. The data on the PES structure including the positions and relative energies of its extrema, curvature in their vicinity, and stationary point interrelations provide the foundation for understanding the spectral properties and reactivity of radical ionic species. Examples of applying the PES study results to experimental data interpretation are given. © 2015 Wiley Periodicals, Inc.

The review shows that a complex multihole structure resulting from the avoided crossing is a common feature of the adiabatic potential energy surfaces (PESes) of various cyclic organic radical ions. Many spectral and chemical properties of the radical ions under consideration can be understood through the investigation of their PESes within the framework of relatively simple quantum chemical methods such as restricted open-shell Hartree–Fock method, Moller–Plesset perturbation theory, and density functional theory.

Actinide compounds are very intriguing objects for the quantum chemistry because, on the one hand, these compounds are of great scientific and technological interest and, on the other hand, quantitative first principle based modeling of their electronic structure is extremely difficult because of strong relativistic effects and complicated electron correlation pattern. The efficiency of high-level all-electron relativistic methods in applications to complex actinide systems of practical interest is questionable and more economical but sufficiently accurate approaches to the studies of such systems are preferable. Recently, generalized relativistic effective core potentials (GRECPs) have been generated for actinides to perform accurate calculations of electronic structure and properties of their compounds with moderate computational cost. The accuracy of different GRECP versions is analyzed in atomic calculations and their applications to molecular and cluster calculations are reviewed. The results are compared with available experimental data and other theoretical studies. © 2015 Wiley Periodicals, Inc.

Actinide compounds are very difficult objects for quantum chemical simulation. Generalized relativistic effective core potentials, recently generated for actinides, define an accurate electronic structure model, offering the possibility to quantitatively predict various properties of actinide compounds with moderate computational efforts. Its accuracy is analyzed and applications to molecular calculations are reviewed.

Organocuprates (II) and (III) are intermediates of catalytic and photochemical reactions; nevertheless, in many cases their structure and reaction ability are unclear. Quantum-chemical calculations performed within the framework of density functional theory allowed to confirm some experimental evidences of existence of such organometallic compounds. In this article, composition and geometry of organocopper transients were estimated via comparing of experimental and calculated energies of electronic transitions and g-tensors. The formation of σ-bond CuC(sp^{3}) in adducts of Cu(I) and Cu(II) complexes with alkyl-type radicals was corroborated by Natural Bonding Orbital analysis. The nuclearity of Cu(II) chloride complexes influences the mechanism of their interaction with alkyl radicals. © 2015 Wiley Periodicals, Inc.

Application of DFT techniques to estimate structures and properties of organocuprates(II) and (III) intermediates of catalytic and photochemical reactions is reviewed. Reasonable agreement of calculated EPR parameters and UV-Vis spectra of organocuprates with experiment allowed not only to determine the composition and geometry of such complexes but also to discuss their electronic properties.

Geminals are counterparts of two-electron chemical bonds and lone pairs in the realm of wave functions. Antisymmetrized products of geminals provide a solid framework for studies of electron pairing in molecular systems. Natural advantages of geminal wave functions such as the correct description of bond breaking and formation make them a powerful model for electronic structure calculations. The concerted efforts to develop geminal-based methods concentrate on increasing their accuracy and universality. The downside is the high computational cost limiting applications to small and toy systems. In contrast, the inherent local structure of optimal geminals opens pathways to development of methods for large systems. In particular, perspectives for linear scaling and hybrid quantum/classical approaches using geminals are discussed. The same principles are proposed for development of computational schemes for covalently bound and molecular crystals. © 2015 Wiley Periodicals, Inc.

Multiconfigurational methods based on geminals effectively account pair electron correlations. The cost of their applications to large systems is prohibitive due to the complexity of geminal variation. Nevertheless, the intrinsic local character of geminals prompts development of fast methods for electronic structure calculations. In particular, linear scaling and hybrid quantum mechanical/molecular mechanical schemes as well as efficient methods for crystals are within reach.

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 work describes a new approach for approximate obtaining the positively defined electronic kinetic energy density (KED) from electron density. KED is presented as a sum of the Weizsäcker KED, which is calculated in terms of electron density exactly, and unknown Pauli KED. The latter is presented via local Pauli potential and Gritsenko–van Leeuwen–Baerends kinetic response potential, to which the second-order gradient expansion is applied. The resulting expression for KED contains only one empirical parameter. The approach allowed to correctly reproduce all the features of KED, and electron localization descriptors as electron localization function and phase-space defined Fisher information density for main types of bonds in molecules and molecular crystals. It is also demonstrated that the method is immediately applicable to derivation of mentioned bonding descriptors from experimental electron density. Herewith the method is significantly free from the drawback of Kirzhnits approximation, which is now commonly accepted for evaluation of the electronic kinetic energy characteristics from precise X-ray diffraction experiment. © 2015 Wiley Periodicals, Inc.

The kinetic energy density (KED) can be extracted from the electron density using local Pauli potential and second-order gradient expansion scheme. This approach is able to correctly reproduce all the features of KED and electron localization descriptors as electron localization function and the phase-space defined Fisher information density for many types of bonds in molecules and crystals. This method can be applied for the derivation of bonding descriptors from experimental electron density.

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Issue information http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fqua.25058Issue information 2015-11-24T23:18:55.840736-05:00 doi:10.1002/qua.25058 John Wiley & Sons, Inc. 10.1002/qua.25058 http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1002%2Fqua.25058 Issue Information ii vi

]]>*N*-Brominated compounds are widely used in synthetic and industrial chemistry. In addition, *N*-brominated species are implicated in the development of numerous inflammatoryrelated diseases. In this study by Robert J. O'Reilly and Amir Karton (DOI: 10.1002/qua.25024), accurate NBr bond dissociation energies for a diverse set of molecules have been obtained by means of the high-level W2 composite protocol. This article focuses on the effect of structure on the strength of NBr bonds toward the formation of free radicals. Additionally, to facilitate the study of other N-brominated species, a large number of more economical theoretical procedures have been assessed for the computation of accurate NBr bond energies.

Quantum tunneling effect in entanglement dynamics between two coupled particles with separable Gaussian initial state is investigated using entangled trajectory molecular dynamics method in terms of the reduced-density linear entropy. It has been presented through showing distinguish contribution of single trajectory to linear entropy between classical trajectory and entangled trajectory with same initial state. We find that quantum tunneling effect makes single trajectory's contribution remarkably decrease under quantum dynamics compared to classical dynamics. The nonlocality of quantum entanglement is presented, and the energy transfer between two coupled particles through quantum correlations and classical ones is also discussed in the end. © 2015 Wiley Periodicals, Inc.

Entanglement dynamics under classical and quantum conditions show remarkable differences. Quantum entanglement has statistical characters with contribution from all trajectories. Quantum tunneling can reduce entanglement between two coupled particles. The nonlocal nature of quantum entanglement can be observed through analysis of the contribution of the individual trajectories.

In this study, the results of structural parameters, electronic structure, and thermodynamic properties of the Zr* _{x}*Y

Some semiconductors can be metallized by doping with transition metal atoms. This is an important physicochemical process, because it allows modulation of electronic and thermodynamic properties of new metallic solid solutions. Modeling helps understanding how the degree of metallization can be controlled by dopant concentration. Since metallization of solid solutions from a compound semiconductor has prompted significant interest recently, insights from simulation can be very useful in the design and manufacture of new electronic devices.

A hierarchical sequence of basis sets along with one long-range corrected functional (CAM-B3LYP) were used to calculate electronic optical rotations (OR) at three wavelengths (355.0, 589.3, and 633.0 nm) of 14 rigid chiral molecules whose experimental values are available in the literature. As the results showed to be sensitive to the basis set quality, complete basis set limits were estimated. Special attention was given to five particularly difficult compounds. In these cases, one verifies that vibrational corrections (taken from the literature) must be added to the CAM-B3LYP equilibrium OR to correct signs. In general, the complete basis set limits reported in this work are in good agreement with the experimental data and with those obtained at a higher level of theory. For some compounds, solvent effects are taken into account by means of the polarizable continuum model. For the solvated systems, the dependence between OR and cavity size is also examined. © 2015 Wiley Periodicals, Inc.

An established approach to deduce the absolute stereochemistry in molecules is to compare theoretical and experimental specific optical rotations. Fourteen rigid chiral molecules were used as a test set to determine the accuracy of optical rotations calculated using the CAM-B3LYP density functional. The results were sensitive to the basis set quality. CAM-B3LYP is proposed as an excellent compromise between accuracy and computational cost in determining absolute configurations of conformationally rigid chiral molecules.

Ability of aroylhydrazones to change conformation upon interaction with light makes them promising candidates for molecular switches. Isomerization can be controlled through complexation with selected metal ions which bind with different affinity. *N*′-[1-(2-hydroxyphenyl)ethyliden]iso-nicotinoylhydrazide (HAPI) is an example of a dual-wavelenght photoswitching molecule, whose complexation with metal ions was recently experimentally investigated (Franks et al. J. Inorg. Chem. 2014, 53, 1397). In this contribution, complexes between HAPI and K^{+}, Ca^{2+}, Mn^{2+}, Fe^{2+}, Fe^{3+}, Cu^{+}, Cu^{2+}, and Zn^{2+} ions were investigated using Density Functional Theory, Natural Bond Order analysis, and Quantum Theory of Atoms in Molecules. The most important parameters that determine complex stability are found to be ion radius and charge transferred from ligands to the ion: smaller ion radii and larger CT values characterize formation of more stable complexes. Our results explain experimentally observed effect of different metal ions on photoisomerization through determination of metal ion affinity (MIA): photoisomerization is inhibited if MIA exceeds 100 kcal/mol; for MIA between 50 and 100 kcal/mol excess of metal ions prevents isomerization, whereas in case of MIA below 50 kcal/mol metal ions have no influence on light–HAPI interaction. © 2015 Wiley Periodicals, Inc.

Light represents a means to control isomerization in photoswitching molecules, which can also be partly or completely inhibited through complexation with metal ions. Density functional theory, natural bond orbital analysis, and quantum theory of atoms in molecules are used to explain and predict complex stability and its response to illumination.

Density functional theory calculations were performed to investigate the complete mechanism and selectivity for asymmetric ring opening cross-metathesis of endic anhydride and propene through a chelated Ru catalyst with nitrato ligand. The preferred mechanism begins with the endic anhydride attacking the catalyst from the “side” position and forming a Ru four-membered ring complex. Subsequently, the endic anhydride isomerizes with another four-membered ring complex via the substituent groups rotating their locations. The ring then ruptures and leads to a Ru-alkylidene complex. Afterward, propene reacts with the Ru-alkylidene complex through a similar pathway, resulting in rapid a cycloaddition reaction, isomerization to undergo cycloreversion, and the release of (Z)- or (E)-olefin homodimers. The overall preferred mechanism is in accordance with the mechanism of a previously reported chelated Ru catalyst containing a carboxylate ligand. The energy barrier of the transition state for cycloreversion differs by 2.72 kcal/mol from (Z)-olefin to (E)-olefin, indicating that the reaction has high Z-selectivity, in accordance with experimental results. Moreover, cycloreversion is the rate-determining step. The turnover frequency for selectivity is analyzed to determine the relationship between the theoretically computed catalytic cycle and its experimental counterpart. The activation strain was also analyzed to illustrate the mechanism from the point of quantum chemistry. All of the methods in this article were performed to explain the preference for Z-olefin, which is attributed to a combination of the steric and electronic effects of the chelated catalyst. Finally, the catalyst is compared with the previously reported chelated Ru catalyst with a carboxylate ligand; results reveal that smaller nitrato sizes lead to higher selectivity efficiency of the catalyst. © 2015 Wiley Periodicals, Inc.

Controlling olefin geometry during asymmetric ring opening cross metathesis while still maintaining high stereoselectivity has challenged chemists in recent years. Density functional theory calculations provide insights into the mechanism of the ring opening reaction in olefin metathesis with Ru catalyst and the nature of its Z-selectivity. Calculations prove that the side-bound attack and Z-selectivity is favored and the elemental step of cycloreversion is found to be the rate-determining step.

Herein, chemical adsorption properties of the thiol-functionalized metallocene molecules [M(C_{5}H_{4}SH)_{2}] on Si(111)-Ag√3×√3 surface were investigated using density functional theory calculation. For this purpose, thiol-modified ferrocene [Fe(C_{5}H_{4}SH)_{2}], osmocene [Os(C_{5}H_{4}SH)_{2}], and ruthenocene [Ru(C_{5}H_{4}SH)_{2}] molecules were attached on the surface via two different binding models. The more favorable chemical binding energies of [Fe(C_{5}H_{4}SH)_{2}], [Os(C_{5}H_{4}SH)_{2}], and [Ru(C_{5}H_{4}SH)_{2}] molecules were calculated as −3.42, −2.15, and −2.00 eV, respectively. The results showed that the adsorption energies of metallocene molecules change independently by increasing the radius of metal ions where on going down the group of the periodic table. The calculated adsorption energies showed that [Fe(C_{5}H_{4}SH)_{2}] molecule was more stable on the Si(111)-Ag√3×√3 surface. By calculating the electronic band structure for metallocene/Si(111)-Ag√3×√3 surfaces, we identified a flat dispersion band in a part of the surface Brillouin zone. © 2015 Wiley Periodicals, Inc.

The chemical adsorption properties of the thiol-functionalized metallocene molecules on the Si(111)-Ag√3×√3 surface have been theoretically investigated for different bindings models using DFT. Calculations revealed that the adsorption energies of these metallocene molecules change independently by increasing the radius of inner core metal atoms. Both functional group and metal ion are important for the position of the molecule on the surface.

Homolytic NBr bond dissociation constitutes the initial step of numerous reactions involving *N*-brominated species. However, little is known about the strength of NBr bonds toward homolytic cleavage. We herein report accurate bond dissociation energies (BDEs) for a set of 18 molecules using the high-level W2 thermochemical protocol. The BDEs (at 298 K) of the species in this set range from 162.2 kJ mol^{−1} (*N*-bromopyrrole) to 260.6 kJ mol^{−1} ((CHO)_{2}NBr). In order to compute BDEs of larger systems, for which W2 theory is not applicable, we have benchmarked a wide range of more economical theoretical procedures. Of these, G3-B3 offers the best performance (root-mean-square deviations = 2.9 kJ mol^{−1}), and using this method, we have computed NBr BDEs for four widely used *N*-brominated compounds. These include (BDEs are given in parentheses): *N*-bromosuccinimide (281.6), *N*-bromoglutarimide (263.2), *N*-bromophthalimide (274.7), and 1,3-dibromo-5,5-dimethylhydantoin (218.2 and 264.8 kJ mol^{−1}). © 2015 Wiley Periodicals, Inc.

*N*-Brominated compounds are widely used in synthetic and industrial chemistry. In addition, *N*-brominated species are implicated in the development of numerous inflammatory-related diseases. This article focuses on the effect of structure on the strength of NBr bonds toward the formation of free radicals. Additionally, to facilitate the study of other *N*-brominated species, a large number of more economical theoretical procedures have been assessed for the computation of accurate NBr bond energies.