title: Dielectric response of periodic systems from quantum Monte Carlo calculations.
abstract: We present a novel approach that allows us 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 wave function, 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.
authors.affiliation: Department of Materials Science and Engineering, MIT, Cambridge, Massachusetts 02139, USA.
authors.forename: P
authors.initials: P
authors.lastname: Umari
authors.forename: A J
authors.initials: AJ
authors.lastname: Willamson
authors.forename: Giulia
authors.initials: G
authors.lastname: Galli
authors.forename: Nicola
authors.initials: N
authors.lastname: Marzari