Extensions To Guided Diffusion Monte Carlo For Excited States

Finney, Jacob M.

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https://hdl.handle.net/2142/116496 Copy

Description

Title

Extensions To Guided Diffusion Monte Carlo For Excited States

Author(s)

Finney, Jacob M.

Contributor(s)

McCoy, Anne B.

Issue Date

2022-06-20

Keyword(s)

Comparing theory and experiment

Abstract

Diffusion Monte Carlo (DMC) is a stochastic method that is used to obtain the ground state energy and ground state wave function of a system of interest. DMC requires a potential energy surface (PES) that describes all degrees of freedom of the system. We have found that the use of guiding functions, functions that describe some of the vibrational degrees of freedom within the system, allow improved sampling of the ground state wave function if the guiding function is chosen carefully.\footnote{Lee, V. G. M. and McCoy, A.B., {\it{J. Phys. Chem. A}} (2019), {\bf{123}}, 37, 8063-8070.} \footnote{Finney, J. M., DiRisio, R. J., McCoy, A.B., {\it{J. Phys. Chem. A}} (2020), {\bf{124}}, 45, 9567-9577} While this enables us to used DMC to study larger systems, to obtain spectra we will also need to calculate the excited state energies and matrix elements of the dipole moment operator involving the ground and excited state wave functions. In this work we explore the use of excited state guiding functions for the evaluation of vibrationally excited states. Specifically, we combine the approaches taken from previous work using ground state guided DMC simulations and fixed-node approaches, which we have used to obtain excited state wave functions from unguided DMC calculations. This approach has been applied to studies of OH stretching vibrations in \chem{H_2O} and \chem{H_3O_2^-} , where comparisons to previous studies can be made. Various approaches for obtaining the intensities from the ground and excited state DMC wave functions are explored.\footnote{Barnett, R. N., Reynolds, P. J., Lester Jr., W. A., {\it{J. Chem. Phys.}} (1992), {\bf{96}}, 2141-2154}

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

eng

Handle URL

https://hdl.handle.net/2142/116496&&

DOI

https://doi.org/10.15278/isms.2022.MJ06

Copyright and License Information

Copyright 2022 held by the authors

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