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Advances in methods and algorithms in a modern quantum chemistry program package

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TLDR
Specific developments discussed include fast methods for density functional theory calculations, linear scaling evaluation of energies, NMR chemical shifts and electric properties, fast auxiliary basis function methods for correlated energies and gradients, equation-of-motion coupled cluster methods for ground and excited states, geminal wavefunctions, embedding methods and techniques for exploring potential energy surfaces.
Abstract
Advances in theory and algorithms for electronic structure calculations must be incorporated into program packages to enable them to become routinely used by the broader chemical community. This work reviews advances made over the past five years or so that constitute the major improvements contained in a new release of the Q-Chem quantum chemistry package, together with illustrative timings and applications. Specific developments discussed include fast methods for density functional theory calculations, linear scaling evaluation of energies, NMR chemical shifts and electric properties, fast auxiliary basis function methods for correlated energies and gradients, equation-of-motion coupled cluster methods for ground and excited states, geminal wavefunctions, embedding methods and techniques for exploring potential energy surfaces.

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Photodissociation dynamics of formaldehyde initiated at the T1/S0 minimum energy crossing configurations.

TL;DR: The minimum energy-crossing configurations and energy of the T(1)/S(0) potentials are identified as a step toward studying the multisurface nature of the photodissociation.
Journal ArticleDOI

Onset of diradical character in small nanosized graphene patches

TL;DR: A family of small graphene patches that have both zigzag and armchair edges that are formally Mobius aromatic multiconfigurational systems are investigated to establish their ground state electronic structure and it is found that elongation of theZigzag edge results in an increase of diradical character whereas elongated of the arm chair edge leads to a decrease of dirAdical character.
Journal ArticleDOI

Molecular mechanism of the Z/E-photoisomerization of hemithioindigo hemistilbene.

TL;DR: Using quantum chemical calculations, it is demonstrated that two Z- and E-isomers exist in the electronic ground state as well as on the S(1) surface, which explains the comparably long lifetime of 38 ps of the excited HTI molecules and the observed low quantum yield of photoswitching.
Journal ArticleDOI

Formic and acetic acid aggregation in the liquid state.

TL;DR: The microscopic structure of neat formic and acetic acid has been measured by neutron diffraction with H/D substitution on SANDALS at the ISIS neutron spallation source and modeled via the empirical potential structure refinement (EPSR) method to provide a three-dimensional model of the system under study compatible with the measured structure factors.
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Charge Transport Across Insulating Self-Assembled Monolayers: Non-equilibrium Approaches and Modeling To Relate Current and Molecular Structure

TL;DR: This work indicates that significant control over SAMs largely composed of nominally insulating groups may be possible when tail groups are used that are significantly larger than those used in the experiments of Yoon et al.1.
References
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Journal ArticleDOI

Density‐functional thermochemistry. III. The role of exact exchange

TL;DR: In this article, a semi-empirical exchange correlation functional with local spin density, gradient, and exact exchange terms was proposed. But this functional performed significantly better than previous functionals with gradient corrections only, and fits experimental atomization energies with an impressively small average absolute deviation of 2.4 kcal/mol.
Journal ArticleDOI

Gaussian basis sets for use in correlated molecular calculations. I. The atoms boron through neon and hydrogen

TL;DR: In this paper, a detailed study of correlation effects in the oxygen atom was conducted, and it was shown that primitive basis sets of primitive Gaussian functions effectively and efficiently describe correlation effects.

疟原虫var基因转换速率变化导致抗原变异[英]/Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

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TL;DR: PfPMP1)与感染红细胞、树突状组胞以及胎盘的单个或多个受体作用,在黏附及免疫逃避中起关键的作�ly.
Journal ArticleDOI

General atomic and molecular electronic structure system

TL;DR: A description of the ab initio quantum chemistry package GAMESS, which can be treated with wave functions ranging from the simplest closed‐shell case up to a general MCSCF case, permitting calculations at the necessary level of sophistication.
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