Direct evaluation of the force constant matrix in quantum Monte Carlo

Abstract

We develop a formalism to directly evaluate the matrix of force constants within a Quantum Monte Carlo calculation. We utilize the matrix of force constants to accurately relax the positions of atoms in molecules and determine their vibrational modes, using a combination of Variational and Diffusion Monte Carlo. The computed bond lengths differ by less than 0.007Å from the experimental results for all four tested molecules. For hydrogen and hydrogen chloride, we obtain fundamental vibrational frequencies within 0.1% of experimental results and ~10 times more accurate than leading computational methods. For carbon dioxide and methane, the vibrational frequency obtained is on average within 1.1% of the experimental result, which is at least 3 times closer than results using Restricted Hartree-Fock and Density Functional Theory with a Perdew-Burke-Ernzerhof (PBE) functional and comparable or better than Density Functional Theory with a semi-empirical functional.

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Cited by in corpus (7)

• Variational and Diffusion Quantum Monte Carlo Calculations with the CASINO Code
• Atomic forces by quantum Monte Carlo: application to phonon dispersion calculation
• Error Cancellation in Diffusion Monte Carlo Calculations of Surface Chemistry
• Phonons of metallic hydrogen with quantum Monte Carlo
• Deep learning quantum Monte Carlo for solids
• Absence of diagonal force constants in cubic Coulomb crystals
• Fast Evaluation of Unbiased Atomic Forces in ab initio Variational Monte Carlo via the Lagrangian Technique