This study reports on the prospect for the routine use of Quantum Monte Carlo (QMC) for the electronic structure problem, applying fixed-node Diffusion Monte Carlo (DMC) to generate highly accurate Born-Oppenheimer potential energy curves (PECs) for small molecular systems. The singlet ground electronic states of CO and N2 were used as test cases. The PECs obtained by DMC employing multiconfigurational trial wavefunctions were compared with those obtained by conventional high-accuracy electronic structure methods such as multireference configuration interaction and/or the best available empirical spectroscopic curves. The goal was to test whether a straightforward procedure using available QMC codes could be applied robustly and reliably. Results obtained with DMC codes were found to be in close agreement with the benchmark PECs, and the n3 scaling with the number of electrons (compared with n7 or worse for conventional high-accuracy quantum chemistry) could be advantageous depending on the system size. Due to a large pre-factor in the scaling, for the small systems tested here, it is currently still much more computationally intensive to compute PECs with QMC. Nevertheless, QMC algorithms are particularly well-suited to large-scale parallelization and are therefore likely to become more relevant for future massively parallel hardware architectures.
A. D. Powell and R. Dawes, "Calculating Potential Energy Curves with Fixed-Node Diffusion Monte Carlo: CO and N2," Journal of Chemical Physics, vol. 145, no. 22, American Institute of Physics (AIP), Jan 2016.
The definitive version is available at https://doi.org/10.1063/1.4971378
Center for High Performance Computing Research
Keywords and Phrases
Electronic States; Electronic Structure; Molecular Physics; Monte Carlo Methods; Quantum Chemistry; Born-Oppenheimer Potentials; Fixed Node Diffusion Monte Carlo; Ground Electronic State; Massively Parallels; Multi Reference Configuration Interactions; Number of Electrons; Potential Energy Curves; Quantum Monte Carlo; Potential Energy
International Standard Serial Number (ISSN)
Article - Journal
© 2016 Andrew D. Powell and Richard Dawes, All rights reserved.