Taming the fixed-node error in diffusion Monte Carlo via range separation

Journal Article · Tue Nov 03 00:00:00 EST 2020 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/5.0026324· OSTI ID:1698207

Scemama, Anthony ; Giner, Emmanuel ; Benali, Anouar ; Loos, Pierre-François

By combining density-functional theory (DFT) and wave function theory via the range separation (RS) of the interelectronic Coulomb operator, we obtain accurate fixed-node diffusion Monte Carlo (FN-DMC) energies with compact multi-determinant trial wave functions. In particular, we combine here short-range exchange-correlation functionals with a flavor of selected configuration interaction known as configuration interaction using a perturbative selection made iteratively (CIPSI), a scheme that we label RS-DFT-CIPSI. One of the take-home messages of the present study is that RS-DFT-CIPSI trial wave functions yield lower fixed-node energies with more compact multi-determinant expansions than CIPSI, especially for small basis sets. Indeed, as the CIPSI component of RS-DFT-CIPSI is relieved from describing the short-range part of the correlation hole around the electron–electron coalescence points, the number of determinants in the trial wave function required to reach a given accuracy is significantly reduced as compared to a conventional CIPSI calculation. Importantly, by performing various numerical experiments, we evidence that the RS-DFT scheme essentially plays the role of a simple Jastrow factor by mimicking short-range correlation effects, hence avoiding the burden of performing a stochastic optimization. Considering the 55 atomization energies of the Gaussian-1 benchmark set of molecules, we show that using a fixed value of μ = 0.5 bohr−1 provides effective error cancellations as well as compact trial wave functions, making the present method a good candidate for the accurate description of large chemical systems.

• Sponsoring Organization: USDOE
• OSTI ID: 1698207
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Vol. 153 Journal Issue: 17; ISSN 0021-9606
• Publisher: American Institute of Physics
• Country of Publication: United States
• Language: English