Journal ArticleDOI
A new, fast, semi-direct implementation of linear scaling local coupled cluster theory
TLDR
In this paper, a new way to compute the external exchange matrices in the local coupled cluster (LCC) theory is presented, which eliminates the most important bottleneck of linear scaling LCC methods.Abstract:
A new way to compute the external exchange matrices in the local coupled cluster (LCC) theory is presented, which eliminates the most important bottleneck of our previous linear scaling LCC methods. It is based on a decomposition of the transformed two-electron integral set involving four external indices into blocks belonging to quadruples of atoms. A new additional transformation module was developed, which generates this very compact 4-external integral set before the LCC iteration loop is entered. The length of this integral set and the computational cost for producing it scale linearly with molecular size. Using these precomputed integrals, their contraction with the amplitudes, i.e. the assembly of the external exchange matrices occurring in each LCC iteration now is performed directly in the (external) space of the projected AOs (AOs, atomic orbitals) rather than in AO basis as previously, and proceeds exceedingly fast (3 min
compared to 15 h with our previous algorithm, for the largest test-molecule considered in this paper).read more
Citations
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Molpro: a general-purpose quantum chemistry program package
TL;DR: Molpro (available at http://www.molpro.net) is a general-purpose quantum chemical program as discussed by the authors, which uses local approximations combined with explicit correlation treatments, highly accurate coupled-cluster calculations are now possible for molecules with up to approximately 100 atoms.
Journal ArticleDOI
Development of density functionals for thermochemical kinetics
A. Daniel Boese,Jan M. L. Martin +1 more
TL;DR: A density functional theory exchange-correlation functional for the exploration of reaction mechanisms is proposed, which has an accuracy in the 2 kcal/mol range for transition state barriers but, unlike previous attempts, this improved accuracy does not come at the expense of equilibrium properties.
Journal ArticleDOI
Fast linear scaling second-order Møller-Plesset perturbation theory (MP2) using local and density fitting approximations
TL;DR: It is demonstrated that for large molecules DF-LMP2 is much faster than either LMP2 or DF-MP2 and the errors arising from local approximations are somewhat larger than expected from calculations on smaller systems.
Journal ArticleDOI
Assessment of the Performance of the M05-2X and M06-2X Exchange-Correlation Functionals for Noncovalent Interactions in Biomolecules.
TL;DR: The highly parametrized, empirical exchange-correlation functionals, M05-2X and M06-2x, developed by Zhao and Truhlar are tested to describe noncovalent interactions better than density functionals which are currently in common use and are compared to a nonempirical density functional, PBE, and also to that of PBE plus Grimme's empirical dispersion correction, PBI.
Journal ArticleDOI
Efficient and accurate local approximations to coupled-electron pair approaches: An attempt to revive the pair natural orbital method
TL;DR: An efficient production level implementation of the closed shell CEPA and CPF methods is reported that can be applied to medium sized molecules and has essentially the same accuracy as parent CEPA (CPF) methods for thermochemistry, kinetics, weak interactions, and potential energy surfaces but is up to 500 times faster.
References
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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.
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A fifth-order perturbation comparison of electron correlation theories
TL;DR: In this paper, a new augmented version of coupled-cluster theory, denoted as CCSD(T), is proposed to remedy some of the deficiencies of previous augmented coupledcluster models.
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A full coupled‐cluster singles and doubles model: The inclusion of disconnected triples
TL;DR: The coupled cluster singles and doubles model (CCSD) as discussed by the authors is derived algebraically, presenting the full set of equations for a general reference function explicitly in spin-orbital form, and the computational implementation of the CCSD model, which involves cubic and quartic terms, is discussed and results are compared with full CI calculations for H2O and BeH2.
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Quadratic configuration interaction. A general technique for determining electron correlation energies
TL;DR: In this article, a general procedure for calculation of the electron correlation energy, starting from a single Hartree-Fock determinant, is introduced, and the relation of this method to coupled-cluster (CCSD) theory is discussed.
Journal ArticleDOI
A fast intrinsic localization procedure applicable for ab initio and semiempirical linear combination of atomic orbital wave functions
János Pipek,Paul G. Mezey +1 more
TL;DR: In this article, a new intrinsic localization algorithm based on a recently developed mathematical measure of localization is proposed, which is adaptable for both ab initio and semi-empirical methods, even in those cases where the exact form of the atomic basis functions is not defined.