Exploring Rovibrational States of Floppy Molecules Using Diffusion Monte Carlo
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Date
2015-05
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The Ohio State University
Abstract
In this work, diffusion Monte Carlo (DMC) methodology was extended to allow for the calculation of rotationally excited states by expansion into a functional space. This new methodology was used to study CH5+ and its deuterated isotopologues. Previous results regarding the localization of deuterium atoms within the H3 subunit are corroborated, and new results regarding the lack of change in the wavefunction upon rotational excitation up to J = 10 are shown. The method was then tested concurrently with the previously established fixed node DMC method on H2D+ and HD2+ , to determine its efficacy in capturing rovibrational coupling. This mixed method was found to produce errors up to 20 cm−1 for states with J = 2 and νasym = 1. Group theory was then used to analyze the cause of the error, and showed the exclusion of Coriolis coupling terms to likely be at fault.
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Keywords
diffusion Monte Carlo, CH5+, rotational excitation, quantum mechanics