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arXiv · 1202.0317

Approaching Chemical Accuracy with Quantum Monte Carlo

F. R. Petruzielo·Julien Toulouse·C. J. Umrigar
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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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F. R. Petruzielo, Julien Toulouse, C. J. Umrigar. 2012-02-01. Approaching Chemical Accuracy with Quantum Monte Carlo. https://doi.org/10.1063/1.3697846

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