Neutral molecules with sufficiently large dipole moments can bind electrons in diffuse nonvalence orbitals, forming so-called dipole-bound anions. Because overall binding energies are often only of the order of tens to hundreds of wave numbers and long-range correlation effects play an important role in the binding of an excess electron, predictively modeling dipole-bound anions remains a challenge. During this talk, I will describe recent work performed in collaboration with Ken that demonstrates how quantum Monte Carlo methods, such as Diffusion Monte Carlo and Auxiliary Field Quantum Monte Carlo, can accurately characterize molecular dipole-bound anions with near threshold dipole moments, despite their inherent approximations to curb the sign/phase problems. We find that, while all of the methods employed can readily distinguish between bound and unbound states, only correlated sampling techniques, such as correlated Auxiliary Field Quantum Monte Carlo, are particularly well-suited for resolving the fine energy differences between the neutral and anionic species. These results shed light on the fundamental limitations of quantum Monte Carlo methods and pave the way toward using them for the study of weakly-bound species that are too large to model using traditional electronic structure methods.

Predicting the electron binding energies of dipole-bound anions via quantum Monte Carlo

2019 Spring National Meeting

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