Full wave function optimization with quantum Monte Carlo and its effect on the dissociation energy of FeS

Abstract

Diffusion quantum Monte Carlo calculations with partial and full optimization of the guide function are carried out for the dissociation of the FeS molecule. For the first time, quantum Monte Carlo orbital optimization for transition metal compounds is performed. It is demonstrated that energy optimization of the orbitals of a complete active space wave function in the presence of a Jastrow correlation function is required to obtain agreement with the experimental dissociation energy. Furthermore, it is shown that orbital optimization leads to a ${}^5\Delta$ ground state, in agreement with experiments, but in disagreement with other high-level ab initio wave function calculations which all predict a ${}^5{\Sigma }^{+}$ ground state. The role of the Jastrow factor in DMC calculations with pseudo potentials is investigated. The results suggest that a large Jastrow factor may improve the DMC accuracy substantially at small additional cost.

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• Spin density distribution in open-shell transition metal systems: A comparative post-Hartree-Fock, Density Functional Theory and quantum Monte Carlo study of the CuCl2 molecule
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Cited by in corpus (4)

• Orbital optimized unitary coupled cluster theory for quantum computer
• Deterministic construction of nodal surfaces within quantum Monte Carlo: the case of FeS
• Taming the fixed-node error in diffusion Monte Carlo via range separation
• Full Wave Function Optimization with Quantum Monte Carlo -- A study of the Dissociation Energies of ZnO, FeO, FeH, and CrS