An excited-state approach within full configuration interaction quantum Monte Carlo

Journal Article · Wed Oct 07 04:00:00 EDT 2015 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.4932595· OSTI ID:22489675

Smart, Simon D. ^[1]; Booth, George H. ^[2]; Alavi, Ali ^[3]

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1. Max Planck Institute for Solid State Research, Heisenbergstraße 1, 70569 Stuttgart (Germany)
2. Department of Physics, King’s College London, Strand, London WC2R 2LS (United Kingdom)
3. University Chemical Laboratory, Lensfield Road, Cambridge CB2 1EW (United Kingdom)

We present a new approach to calculate excited states with the full configuration interaction quantum Monte Carlo (FCIQMC) method. The approach uses a Gram-Schmidt procedure, instantaneously applied to the stochastically evolving distributions of walkers, to orthogonalize higher energy states against lower energy ones. It can thus be used to study several of the lowest-energy states of a system within the same symmetry. This additional step is particularly simple and computationally inexpensive, requiring only a small change to the underlying FCIQMC algorithm. No trial wave functions or partitioning of the space is needed. The approach should allow excited states to be studied for systems similar to those accessible to the ground-state method due to a comparable computational cost. As a first application, we consider the carbon dimer in basis sets up to quadruple-zeta quality and compare to existing results where available.

• OSTI ID: 22489675
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 13 Vol. 143; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ALGORITHMS
CARBON
COMPARATIVE EVALUATIONS
CONFIGURATION INTERACTION
DIMERS
EXCITED STATES
GROUND STATES
MONTE CARLO METHOD
STOCHASTIC PROCESSES