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Multi-Determinant Trial Functions in the Determination of the Dissociation Energy of the Beryllium Dimer: A Quantum Monte Carlo Study

Published

Author(s)

J A. Harkless, Karl Irikura

Abstract

Both variational Monte Carlo (VMC) and fixed-node diffusion Monte Carlo (DMC) are used to estimate the dissociation energy of Be2. The effect of using single- and multi-reference trial functions on the quality of the Monte Carlo estimates is investigated, with independent-particle wavefunctions ranging from a restricted Hartree-Fock (RHF) calculation up to a complete active space self-consistent field (CASSCF) with four valence electrons in twelve active orbitals. It was determined that the best trial function for DMC had a high cutoff for inclusion and included all 2s and 2p orbitals in a CASSCF(4,8) calculation. The best DMC estimate, De= 829(64) cm-1, compares well with the experimental value of 839(10) cm-1 but is lower than values from the best basis-set calculations.
Citation
International Journal of Quantum Chemistry
Volume
106
Issue
No. 11

Keywords

ab initio, beryllium, dissociation energy, QMC, quantum monte carlo, trial function

Citation

Harkless, J. and Irikura, K. (2006), Multi-Determinant Trial Functions in the Determination of the Dissociation Energy of the Beryllium Dimer: A Quantum Monte Carlo Study, International Journal of Quantum Chemistry (Accessed April 23, 2024)
Created August 31, 2006, Updated October 12, 2021