Towards chemical accuracy using the Jastrow correlated antisymmetrized geminal power ansatz

TL;DR

This paper demonstrates that the Jastrow correlated antisymmetrized geminal power (JsAGPs) ansatz, combined with lattice regularized diffusion Monte Carlo, achieves near chemical accuracy in atomization energy calculations for a set of molecules, outperforming traditional methods.

Contribution

The study introduces the JsAGPs ansatz as a more flexible and efficient wave function form for electronic structure calculations, achieving high accuracy in atomization energies.

Findings

Achieved chemical accuracy (~1 kcal/mol) for many molecules.

Obtained a mean absolute deviation of 1.6 kcal/mol with JsAGPs.

Outperformed JDFT ansatz in accuracy.

Abstract

Herein, we report accurate atomization energy calculations for 55 molecules in the Gaussian-2 (G2) set using lattice regularized diffusion Monte Carlo (LRDMC). We compare the Jastrow-Slater determinant ansatz with a more flexible JsAGPs (Jastrow correlated antisymmetrized geminal power with singlet correlation) ansatz. AGPs is built from pairing functions, which explicitly include pairwise correlations among electrons and hence, this ansatz is expected to be more efficient in recovering the correlation energy. The AGPs wave functions are first optimized at the variational Monte Carlo (VMC) level, which includes both the Jastrow factor and the nodal surface optimization. This is followed by the LRDMC projection of the ansatz. Remarkably, for many molecules, the LRDMC atomization energies obtained using the JsAGPs ansatz reach chemical accuracy ($\sim$1 kcal/mol) and for most other molecules, the atomization energies are accurate within $\sim$5 kcal/mol. We obtained a mean absolute deviation of 1.6 kcal/mol with JsAGPs and 3.2 kcal/mol with JDFT (Jastrow factor + Slater determinant with DFT orbitals) ansatz. This work shows the effectiveness of the flexible AGPs ansatz for atomization energy calculations and electronic structure simulations in general.