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Journal Articles The Journal of Chemical Physics Year : 2012

Approaching chemical accuracy with quantum Monte Carlo

Abstract

A quantum Monte Carlo study of the atomization energies for the G2 set of molecules is presented. Basis size dependence of diffusion Monte Carlo atomization energies is studied with a single determinant Slater-Jastrow trial wavefunction formed from Hartree-Fock orbitals. With the largest basis set, the mean absolute deviation from experimental atomization energies for the G2 set is 3.0 kcal/mol. Optimizing the orbitals within variational Monte Carlo improves the agreement between diffusion Monte Carlo and experiment, reducing the mean absolute deviation to 2.1 kcal/mol. Moving beyond a single determinant Slater-Jastrow trial wavefunction, diffusion Monte Carlo with a small complete active space Slater-Jastrow trial wavefunction results in near chemical accuracy. In this case, the mean absolute deviation from experimental atomization energies is 1.2 kcal/mol. It is shown from calculations on systems containing phosphorus that the accuracy can be further improved by employing a larger active space.
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Dates and versions

hal-00974223 , version 1 (05-04-2014)

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Frank R. Petruzielo, Julien Toulouse, C. J. Umrigar. Approaching chemical accuracy with quantum Monte Carlo. The Journal of Chemical Physics, 2012, 136, pp.124116. ⟨10.1063/1.3697846⟩. ⟨hal-00974223⟩
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