Multi-Determinant Trial Functions in the Determination of the Dissociation Energy of the Beryllium Dimer: A Quantum Monte Carlo Study
J A. Harkless, Karl Irikura
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.
International Journal of Quantum Chemistry
ab initio, beryllium, dissociation energy, QMC, quantum monte carlo, trial function
and Irikura, K.
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 May 29, 2023)