The Classical-Map Hyper-Netted-Chain (CHNC) method and associated novel density-functional methods for Warm Dense Matter

TL;DR

This paper introduces the Classical-Map Hyper-Netted-Chain (CHNC) method and related density-functional approaches to model warm dense matter, addressing complex many-body interactions in non-equilibrium quantum systems.

Contribution

It develops a classical mapping technique for quantum electron gases and integrates it with CHNC and CMMD methods for efficient calculation of pair-distribution functions in warm dense matter.

Findings

CHNC efficiently computes PDFs for uniform systems.

Classical map accurately approximates quantum correlations.

Applications include quantum fluids, plasmas, and quantum dots.

Abstract

The advent of short-pulse lasers, nanotechnology, as well as shock-wave techniques have created new states of matter (e.g., warm dense matter) that call for new theoretical tools. Ion correlations, electron correlations as well as bound states, continuum states, partial degeneracies and quasi-equilibrium systems need to be addressed. Bogoliubov's ideas of timescales can be used to discuss the quasi-thermodynamics of non-equilibrium systems. A rigorous approach to the associated many-body problem turns out to be the computation of the underlying pair-distribution functions g_ee, g_ei and g_ii, that directly yield non-local exchange-correlation potentials, free energies etc., valid within the timescales of each evolving system. An accurate classical map of the strongly-quantum uniform electron-gas problem given by Dharma-wardana and Perrot is reviewed. This replaces the quantum electrons at T=0 by an equivalent classical fluid at a finite temperature T_q, and having the same correlation energy. It has been shown, but not proven, that the classical fluid g_ij are excellent approximations to the quantum g_ij. The classical map is used with classical molecular dynamics (CMMD) or hyper-netted-chain integral equations (CHNC) to determine the pair-distribution functions (PDFs), and hence their thermodynamic and linear transport properties. The CHNC is very efficient for calculating the PDFs of uniform systems, while CMMD is more adapted to non-uniform systems. Applications to 2D and 3D quantum fluids, Si metal-oxide-field-effect transistors, Al plasmas, shock-compressed deuterium, two-temperature plasmas, pseudopotentials, as well as calculations for parabolic quantum dots are reviewed.