Dielectric Response of Periodic Systems from Quantum Monte Carlo Calculations

TL;DR

This paper introduces a new quantum Monte Carlo method to accurately compute the dielectric response of periodic systems using a Berry-phase approach, validated on hydrogen systems.

Contribution

A novel quantum Monte Carlo approach for dielectric response in periodic systems using a Berry-phase formulation and self-consistent Hamiltonian.

Findings

Validated on hydrogen atom with accurate results.

Applied to hydrogen chains with excellent agreement to quantum chemistry.

Demonstrated effectiveness of the method for periodic systems.

Abstract

We present a novel approach that allows to calculate the dielectric response of periodic systems in the quantum Monte Carlo formalism. We employ a many-body generalization for the electric enthalpy functional, where the coupling with the field is expressed via the Berry-phase formulation for the macroscopic polarization. A self-consistent local Hamiltonian then determines the ground-state wavefunction, allowing for accurate diffusion quantum Monte Carlo calculations where the polarization's fixed point is estimated from the average on an iterative sequence, sampled via forward-walking. This approach has been validated for the case of an isolated hydrogen atom, and then applied to a periodic system, to calculate the dielectric susceptibility of molecular-hydrogen chains. The results found are in excellent agreement with the best estimates obtained from the extrapolation of quantum-chemistry calculations.