Full Configuration Interaction Quantum Monte Carlo and Diffusion Monte Carlo: A Comparative Study of the 3D Homogeneous Electron Gas
ORAL
Abstract
Full configuration interaction quantum Monte Carlo$^1$ (FCIQMC) and its initiator adaptation$^2$ allow for exact solutions to the Schr\"odinger equation to be obtained within a finite-basis wavefunction \textit{ansatz}. In this talk, we explore an application of FCIQMC to the homogeneous electron gas (HEG). In particular we use these exact finite-basis energies to compare with approximate quantum chemical calculations from the VASP code$^3$. After removing the basis set incompleteness error by extrapolation$^{4,5}$, we compare our energies with state-of-the-art diffusion Monte Carlo calculations from the CASINO package$^6$. Using a combined approach of the two quantum Monte Carlo methods, we present the highest-accuracy thermodynamic (infinite-particle) limit energies for the HEG achieved to date. $^1$ G. H. Booth, A. Thom, and A. Alavi, J. Chem. Phys. 131, 054106 (2009). $^2$ D. Cleland, G. H. Booth, and A. Alavi, J. Chem. Phys. 132, 041103 (2010). $^3$ www.vasp.at (2012). $^4$ J. J. Shepherd, A. Gr\"uneis, G. H. Booth, G. Kresse, and A. Alavi, Phys. Rev. B. 86, 035111 (2012). $^5$ J. J. Shepherd, G. H. Booth, and A. Alavi, J. Chem. Phys. 136, 244101 (2012). $^6$ R. Needs, M. Towler, N. Drummond, and P. L. R\'ios, J. Phys.: Condensed Matter 22, 023201 (2010).
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