Scalable multi-reference chemistry using quantum Monte Carlo

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• Dr Nick Blunt, Riverlane
• Wednesday 24 November 2021, 14:30-15:30
• Zoom and Dept of Chemistry, Wolfson Lecture Theatre.

If you have a question about this talk, please contact Lisa Masters.

https://zoom.us/j/93027947380?pwd=TTIrV3hPaFV4SlRyZm85UHF0d0RxUT09 Meeting ID: 930 2794 7380 Passcode: 697350

In quantum chemistry we have many scalable methods for the accurate treatment of single-reference problems, notably including density functional theory and coupled cluster theory. However, these methods are less reliable when applied to strongly multi-reference problems. In such cases, a common approach is to perform a complete active space (CAS) procedure followed by perturbation theory. However, solving this CAS problem is challenging beyond small active spaces. In this talk, we will investigate variational Monte Carlo (VMC) and the fixed-node approximation as an approach for solving the active space problem. Specifically, we will use VMC to optimise Jastrow mean-field wave functions, which can provide an efficient representation of multi-reference states. We then investigate full configuration interaction quantum Monte Carlo (FCIQMC) as a method to improve the accuracy of these VMC solutions further, and investigate the scaling of this approach.

This talk is part of the Theory - Chemistry Research Interest Group series.

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