International Journal of Quantum Chemistry

Cover image for Vol. 115 Issue 13

Early View (Online Version of Record published before inclusion in an issue)

Online ISSN: 1097-461X

Associated Title(s): Journal of Computational Chemistry

VIEW

  1. 1 - 20
  2. 21 - 40
  1. Full Papers

    1. A numerical solution of the pair equation of a model two-electron diatomic system

      Khaled Bodoor, Jacek Kobus and John Morrison

      Article first published online: 20 APR 2015 | DOI: 10.1002/qua.24921

      Thumbnail image of graphical abstract

      A novel, numerical method is presented for the solution of the five-variable pair equation for a model two-electron diatomic molecule. It extends previous work on solving Fock equations for diatomic molecules discretized on two-variable grids. Solutions of such equations which include the term inline image explicitly, the so-called pair functions, can be used to evaluate coupled-cluster diagrams to recover a significant fraction of the dynamic correlation energy for diatomic molecules.

    2. Crystal structure representations for machine learning models of formation energies

      Felix Faber, Alexander Lindmaa, O. Anatole von Lilienfeld and Rickard Armiento

      Article first published online: 20 APR 2015 | DOI: 10.1002/qua.24917

      Thumbnail image of graphical abstract

      Feature vector representations of crystal structures for machine learning models of formation energies of solids are evaluated. A representation previously found successful for molecules is generalized to periodic systems in three different ways. For training sets of 3000 crystal structures comprising all different elements, the best representation is estimated to predict formation energies of new materials with an average error of 0.37 eV/atom.

  2. Perspective

    1. You have full text access to this OnlineOpen article
      QCTFF: On the construction of a novel protein force field

      Paul L. A. Popelier

      Article first published online: 13 MAR 2015 | DOI: 10.1002/qua.24900

      Thumbnail image of graphical abstract

      A novel protein force called QCTFF is parameterised without using the familiar force field expression of bonded and non-bonded interactions. Instead, it overhauls this architecture and directly captures the behaviour of an atom while interacting with other atoms. The machine learning method kriging is trained to predict four fundamental energy contributions: (i) atomic self-energy, (ii) Coulomb energy, (iii) exchange energy and (iv) correlation energy. Multipole moment represents the medium to long-range electrostatics.

  3. Erratum

    1. You have free access to this content
      Erratum: On spin wavefunctions and young orthogonal matrices

      Vladimir A. Yurovsky

      Article first published online: 6 MAR 2015 | DOI: 10.1002/qua.24893

      This article corrects:

      On spin wavefunctions and young orthogonal matrices

      Vol. 113, Issue 10, 1436–1439, Article first published online: 12 OCT 2012

  4. Tutorial Reviews

    1. You have free access to this content
      Constructing high-dimensional neural network potentials: A tutorial review

      Jörg Behler

      Article first published online: 6 MAR 2015 | DOI: 10.1002/qua.24890

      Thumbnail image of graphical abstract

      In this tutorial review, a method to construct high-dimensional interatomic potentials employing artificial neural networks is reviewed. This approach allows to carry out molecular dynamics simulations of large systems containing thousands of atoms with close to first-principles accuracy hand has been applied successfully to a number of different systems including metals, semiconductors, oxides, and molecular clusters. A strong focus of the review is on practical aspects of constructing these potentials.

  5. Review

    1. You have free access to this content
      A general method to describe intersystem crossing dynamics in trajectory surface hopping

      Sebastian Mai, Philipp Marquetand and Leticia González

      Article first published online: 6 MAR 2015 | DOI: 10.1002/qua.24891

      Thumbnail image of graphical abstract

      Intersystem crossing mediated by spin-orbit coupling provides, together with internal conversion, a way for molecules to lose energy non-radiatively. For large molecular systems, trajectory surface hopping theories have become very popular to study excited-state dynamics, but only recently, interest in surface hopping methods incorporating spin-orbit interaction couplings has emerged. This paper describes SHARC, a generally applicable and accurate trajectory surface hopping method to describe intersystem crossing dynamics.

  6. Full Papers

    1. A fast charge-Dependent atom-pairwise dispersion correction for DFTB3

      Riccardo Petraglia, Stephan N. Steinmann and Clemence Corminboeuf

      Article first published online: 26 FEB 2015 | DOI: 10.1002/qua.24887

      Thumbnail image of graphical abstract

      dDMC is a novel atom-pairwise dispersion correction that is compatible with self-consistent charge density functional tight binding (SCC-DFTB). dDMC relies upon the use of Mulliken charges that are readily available from the DFTB computations at no additional cost. The performance of dDMC is validated on series of examples targeting energies, geometries and molecular dynamic trajectories of π-π stacked motifs featuring sulfur-containing molecules that are known to be especially challenging for DFTB.

  7. Perspective

    1. You have free access to this content
      Modeling absorption and fluorescence solvatochromism with QM/Classical approaches

      Benedetta Mennucci

      Article first published online: 26 FEB 2015 | DOI: 10.1002/qua.24889

      Thumbnail image of graphical abstract

      Solvatochromism is a very complex phenomenon which manifests the modifications induced in the electronic states of molecular systems by the environment. Nowadays, solvatochromism can be successfully simulated with multiscale approaches combining a quantum mechanical description of the chromophoric probe and classical models for the environment.

  8. Reviews

    1. You have free access to this content
      Quantum chemical studies of asymmetric reactions: Historical aspects and recent examples

      Kathrin H. Hopmann

      Article first published online: 18 FEB 2015 | DOI: 10.1002/qua.24882

      Thumbnail image of graphical abstract

      Quantum mechanical methods are nowadays widely employed to study asymmetric reactions. This review presents a historic perspective, from one of the first single-point HF/STO-3G studies reported in the 1970s to current DFT approaches involving non-truncated structures, diastereomeric reaction pathways, and free energies with solvent and dispersion corrections. The reactions discussed include nucleophilic addition, amine-catalyzed aldol reactions, osmium-catalyzed dihydroxylation, and rhodium-, ruthenium-, and iridium-catalyzed hydrogenations.

  9. Perspective

    1. You have free access to this content
      How quantum chemistry can solve fundamental problems in bioenergetics

      Margareta R. A. Blomberg

      Article first published online: 24 JAN 2015 | DOI: 10.1002/qua.24868

      Thumbnail image of graphical abstract

      Cellular energy conservation and energy storage processes are important in all forms of life. Quantum chemical calculations can provide fundamental insight into the mechanisms of enzymes involved in cellular energy conservation. Large molecular models of the active sites of such enzymes are used to construct free energy profiles. From the energy profiles, conclusions are drawn about mechanisms and structures, and experimental puzzles are solved.

  10. Review

    1. You have free access to this content
      Magic state distillation and gate compilation in quantum algorithms for quantum chemistry

      Colin J. Trout and Kenneth R. Brown

      Article first published online: 24 JAN 2015 | DOI: 10.1002/qua.24856

      Thumbnail image of graphical abstract

      Quantum chemistry algorithms on a quantum computer map the molecular Hamiltonian to a spin Hamiltonian. The dynamics of the Hamiltonian are then simulated using a set of elementary operations. Fault-tolerant protocols limit the set of operations and implementation of certain operations requires ancillary resource states, known as magic states. Recent developments that have improved the efficiency of magic state preparation and the compilation of arbitrary gates from discrete gate sets are reviewed.

  11. Full Papers

    1. Entanglement creation in Compton scattering of neutrons on protons and its possible energetic consequences

      Erik B. Karlsson

      Article first published online: 12 JAN 2015 | DOI: 10.1002/qua.24862

      Thumbnail image of graphical abstract

      The possible energetic consequences of quantum entanglement are investigated, using p-n scattering as an example. It is first calculated (for the first time for a realistic case) how the entanglement arises during the interaction of the neutron and the proton and how it decays with the separation of the particles. In the entanglement process, energy is lost through virtual excitation of a compound deuteron state, resulting in a lowering of energy.

    2. Adaptive machine learning framework to accelerate ab initio molecular dynamics

      Venkatesh Botu and Rampi Ramprasad

      Article first published online: 23 DEC 2014 | DOI: 10.1002/qua.24836

      Thumbnail image of graphical abstract

      The dynamical atomic-level evolution of typical chemical processes extends to timescales longer than nanoseconds—hard to access routinely using present ab initio methods. Here, an adaptive machine learning framework is proposed to significantly accelerate ab initio molecular dynamics simulations. The scheme learns to predict energies and atomic forces with unprecedented speed and accuracy from an initial ab initio dataset, and systematically expands its predictive capability on-the-fly by including newly encountered chemical environments in its training.

    3. Dynamical entanglement of stretching–stretching and stretching–bending vibrations in SO2

      Liangjun Zhai and Yujun Zheng

      Article first published online: 17 DEC 2014 | DOI: 10.1002/qua.24848

      Thumbnail image of graphical abstract

      The stretching–stretching and stretching–bending vibrations in the triatomic molecule SO2 are investigated as possible building blocks of a bipartite qubit system. The remaining stretching or bending vibrational mode is one resource of intramolecular decoherence. Because of the strong coupling between vibrational modes in SO2, the decoherence process of stretching–bending vibrations is very serious. The stretching–stretching vibrational entanglement is estimated to be more robust, and thus more suitable for the construction of qubits.

  12. Perspective

    1. You have free access to this content
      Orbital entanglement in quantum chemistry

      Katharina Boguslawski and Paweł Tecmer

      Article first published online: 13 DEC 2014 | DOI: 10.1002/qua.24832

      Thumbnail image of graphical abstract

      Quantum information theory provides tools to quantify the interaction of orbitals and allows us to measure the correlation between orbital pairs beyond the qualitative picture of molecular orbital theory. Orbital entanglement offers an alternative perspective to well-established concepts in chemistry and facilitates an understanding of electronic structures and how they change in chemical processes.

  13. Full Papers

    1. The effects of resonance delocalization and the extent of π system on ionization energies of model fluorescent proteins chromophores

      Julia Lazzari-Dean, Anna I. Krylov and Ksenia B. Bravaya

      Article first published online: 2 DEC 2014 | DOI: 10.1002/qua.24825

      Thumbnail image of graphical abstract

      Redox-active fluorescent proteins (FPs) are significant to many bioimaging applications and protein engineering efforts. Theoretical studies reveal strong effects of the OH-group position and the size of the π- conjugated system on the relative energies of the ground and electron-detached states of the chromophores. The effects of phenolate OH-group position on vertical ionization/detachment energies, as well as spin and charge delocalization, highlight the importance of resonance stabilization and substituent electronegativity in determining oxidation energetics.

    2. Shannon entropy and many-electron correlations: Theoretical concepts, numerical results, and Collins conjecture

      Luigi Delle Site

      Article first published online: 28 NOV 2014 | DOI: 10.1002/qua.24823

      Thumbnail image of graphical abstract

      Links between the electron density of DFT and the many-body wavefunctions/correlations are put forward in terms of encoding/decoding concepts of information theory. In particular, the concept of Shannon entropy can be employed into the development of electronic correlation functionals, and the Hohenberg−Kohn theorem be seen as a specific case of a more general encoding process.

    3. Fisher and Shannon information in orbital-free density functional theory

      Ágnes Nagy

      Article first published online: 15 NOV 2014 | DOI: 10.1002/qua.24812

      Thumbnail image of graphical abstract

      Information theory concepts are getting traction in both physics and chemistry. Very relevant for density function theory is the relationship established between the quantum mechanical kinetic energy functional and Fisher information. The Shannon information has instead proved to be a very useful tool in analyzing atoms and molecules. In this article, the Euler equation (independent from the number of electrons) of the orbital-free density functional theory is reformulated with the Shannon and Fisher information.

  14. Reviews

    1. You have free access to this content
      Neural network-based approaches for building high dimensional and quantum dynamics-friendly potential energy surfaces

      Sergei Manzhos, Richard Dawes and Tucker Carrington

      Article first published online: 6 OCT 2014 | DOI: 10.1002/qua.24795

      Thumbnail image of graphical abstract

      Neural Network-based methods for potential energy surface (NN PESs) fitting can be considered “black box” in that they do not impose any predefined functional form, and thus are very portable. However, their main disadvantage is that their accuracy is guaranteed only for a sufficiently high density of fitting points. In this case, NN PESs are arguably very accurate for small molecules and as good as other fitting methods for larger molecules.

  15. Perspective

    1. You have free access to this content
      Phase/current information descriptors and equilibrium states in molecules

      Roman F. Nalewajski

      Article first published online: 10 SEP 2014 | DOI: 10.1002/qua.24750

      Thumbnail image of graphical abstract

      Information-theoretic description of electronic states requires the classical (probability) descriptors and their nonclassical (current) complements. The unconstrained extremum of the resultant entropy/information content determines the phase-transformed equilibrium state, which differs from the stationary (zero-current) state of quantum mechanics. The nonclassical supplements to the familiar classical measures, global (Shannon), and local (Fisher), are designed and current promotion of molecular fragments is explored. This fully quantum information-theoretic approach generates thermodynamic perspective on time evolution of equilibrium states.

VIEW

  1. 1 - 20
  2. 21 - 40

SEARCH

SEARCH BY CITATION