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Analytic nuclear forces and molecular properties from full configuration interaction quantum Monte Carlo

Thomas, Robert E., Opalka, Daniel, Overy, Catherine, Knowles, Peter J., Alavi, Ali and Booth, George H. 2015. Analytic nuclear forces and molecular properties from full configuration interaction quantum Monte Carlo. Journal of Chemical Physics 143 (5) , 054108. 10.1063/1.4927594

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Unbiased stochastic sampling of the one- and two-body reduced density matrices is achieved in full configuration interaction quantum Monte Carlo with the introduction of a second, “replica” ensemble of walkers, whose population evolves in imaginary time independently from the first and which entails only modest additional computational overheads. The matrices obtained from this approach are shown to be representative of full configuration-interaction quality and hence provide a realistic opportunity to achieve high-quality results for a range of properties whose operators do not necessarily commute with the Hamiltonian. A density-matrix formulated quasi-variational energy estimator having been already proposed and investigated, the present work extends the scope of the theory to take in studies of analytic nuclear forces, molecular dipole moments, and polarisabilities, with extensive comparison to exact results where possible. These new results confirm the suitability of the sampling technique and, where sufficiently large basis sets are available, achieve close agreement with experimental values, expanding the scope of the method to new areas of investigation.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Advanced Research Computing @ Cardiff (ARCCA)
Subjects: Q Science > QD Chemistry
Publisher: American Institute of Physics
ISSN: 0021-9606
Date of First Compliant Deposit: 30 March 2016
Date of Acceptance: 19 July 2015
Last Modified: 07 Dec 2020 16:59

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