Unbiased reduced density matrices and electronic properties from full configuration interaction quantum Monte Carlo.
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Publication Date
2014-12-28Journal Title
J Chem Phys
ISSN
0021-9606
Publisher
AIP Publishing
Volume
141
Issue
24
Pages
244117
Language
eng
Type
Article
Physical Medium
Print
Metadata
Show full item recordCitation
Overy, C., Booth, G. H., Blunt, N., Shepherd, J. J., Cleland, D., & Alavi, A. (2014). Unbiased reduced density matrices and electronic properties from full configuration interaction quantum Monte Carlo.. J Chem Phys, 141 (24), 244117. https://doi.org/10.1063/1.4904313
Abstract
Properties that are necessarily formulated within pure (symmetric) expectation values are difficult to calculate for projector quantum Monte Carlo approaches, but are critical in order to compute many of the important observable properties of electronic systems. Here, we investigate an approach for the sampling of unbiased reduced density matrices within the full configuration interaction quantum Monte Carlo dynamic, which requires only small computational overheads. This is achieved via an independent replica population of walkers in the dynamic, sampled alongside the original population. The resulting reduced density matrices are free from systematic error (beyond those present via constraints on the dynamic itself) and can be used to compute a variety of expectation values and properties, with rapid convergence to an exact limit. A quasi-variational energy estimate derived from these density matrices is proposed as an accurate alternative to the projected estimator for multiconfigurational wavefunctions, while its variational property could potentially lend itself to accurate extrapolation approaches in larger systems.
Sponsorship
Engineering and Physical Sciences Research Council (EP/J003867/1)
Identifiers
External DOI: https://doi.org/10.1063/1.4904313
This record's URL: https://www.repository.cam.ac.uk/handle/1810/285074
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http://www.rioxx.net/licenses/all-rights-reserved
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