Molecular dynamic simulations with radiation

Abstract

Hot dense radiative (HDR) plasmas common to inertial confinement fusion (ICF) and stellar interiors have high temperature (a few hundred eV to tens of keV), high density (tens to hundreds of g/cc) and high pressure (hundreds of Megabars to thousands of Gigabars). Typically, such plasmas undergo collisional, radiative, atomic and possibly thermonuclear processes. In order to describe HDR plasmas, computational physicists in ICF and astrophysics use atomic-scale microphysical models implemented in various simulation codes. Experimental validations of the models used for describing HDR plasmas are difficult to perform. Direct numerical simulation (DNS) of the many-body interactions of plasmas is a promising approach to model validation, but previous work either relies on the collisionless approximation or ignores radiation. We present a first attempt at a new numerical simulation technique to address a currently unsolved problem: the extension of molecular dynamics to collisional plasmas including emission and absorption of radiation. The new technique passes a key test: it relaxes to a blackbody spectrum for a plasma in local thermodynamic equilibrium. This new tool also provides a method for assessing the accuracy of energy and momentum exchange models in hot dense plasmas. As an example, we simulate the evolution of non-equilibrium electron, ion and radiation temperatures for a hydrogen plasma using the new molecular dynamics simulation capability.