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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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Electronic structure of the benzene dimer cation.

TL;DR: The benzene and benzene dimer cations are studied using the equation-of-motion coupled-cluster model with single and double substitutions for ionized systems, suggesting a reassignment of the local excitation peaks in the gas phase experimental spectrum.
Journal ArticleDOI

Excited state non-adiabatic dynamics of pyrrole: A time-resolved photoelectron spectroscopy and quantum dynamics study

TL;DR: Time-resolved photoelectron spectra at a pump wavelength of 217 nm are presented alongside detailed quantum dynamics calculations that suggest that population of the B1(πσ(∗)) state may occur directly when pyrrole is excited at energies in the near UV part of its electronic spectrum.
Journal ArticleDOI

Selection and Validation of Charge and Lennard-Jones Parameters for QM/MM Simulations of Hydrocarbon Interactions with Zeolites.

TL;DR: It is demonstrated that the charges and Lennard-Jones parameters on Si and O must be chosen properly for QM/MM calculations of adsorption energies and activation energies to agree closely with full QM calculations.
Journal ArticleDOI

Symmetric versus asymmetric discretization of the integral equations in polarizable continuum solvation models

TL;DR: In this article, the authors demonstrate cases where solvation energies differ by as much as 24 kcal/mol among these variants, and these differences are sometimes exacerbated by new discretization procedures that guarantee smooth potential energy surfaces.
Journal ArticleDOI

Absorption spectrum, mass spectrometric properties, and electronic structure of 1,2-benzoquinone.

TL;DR: Computational studies of the electronic structures of 1,2-benzoquinone, its proton and hydride ion adducts, and 1,1-benzosemiquinone radical anion indicate that the hydrid adduct is the proton adduct of a doubly negatively charged 1, 2-benzosquinone.
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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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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