Accurate rotational barrier calculations with diffusion quantum Monte Carlo

[Display omitted] •Accurate quantum Monte Carlo calculations of barrier heights.•Perfect agreement of quantum Monte Carlo and coupled cluster results.•Substantial disagreement of calculated and experimentally derived barriers in two cases. Accurate quantum Monte Carlo, MP2, coupled cluster, and DFT...

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Bibliographic Details
Published in:Chemical physics letters 2014-04, Vol.600, p.7-9
Main Authors: Klahm, Sebastian, Lüchow, Arne
Format: Article
Language:English
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Summary:[Display omitted] •Accurate quantum Monte Carlo calculations of barrier heights.•Perfect agreement of quantum Monte Carlo and coupled cluster results.•Substantial disagreement of calculated and experimentally derived barriers in two cases. Accurate quantum Monte Carlo, MP2, coupled cluster, and DFT calculations of rotational barriers of several small molecules are presented. With the diffusion quantum Monte Carlo method (DMC) excellent agreement with experimental barriers is obtained except for the gauche–gauche barriers of n-butane and ethylmethylether. It is argued that these two experimental values might be erroneous. Additionally, barriers calculated with the more efficient variational quantum Monte Carlo method (VMC) are presented. The VMC barriers are less accurate than the DMC results, but it is demonstrated that accurate barriers can be obtained with sophisticated Jastrow correlation functions.
ISSN:0009-2614
1873-4448
DOI:10.1016/j.cplett.2014.03.044