Dipole-bound anions are molecules with sufficiently large dipole moments that they can bind electrons in diffuse nonvalence orbitals far from their nuclei. Because the strength with which they bind their electrons is often of the order of tens to hundreds of wave numbers and because long-range correlation effects often play a key role in their binding ability, predictively modeling dipole-bound anions remains a challenge for many conventional electronic structure methods. In this work, we demonstrate that, despite their inherently stochastic nature and approximations to curb the sign/phase problem, quantum Monte Carlo methods can accurately characterize molecular dipole-bound anions even with near threshold binding energies. We also find that correlated sampling Auxiliary Field Quantum Monte Carlo is particularly well-suited for capturing the fine energy differences needed to resolve dipole-bound anion electron binding energies. 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 too large to model using more expensive wave function techniques, such as those recently demonstrated to contribute to the diffuse interstellar bands.

Accurate predictions of electron binding energies of dipole-bound anions via quantum Monte Carlo methods

2019 Spring National Meeting

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