The influence of defects on the thermal conductivity of compressed LiF

TL;DR

This paper uses molecular dynamics simulations and Green-Kubo techniques to model how defects affect the thermal conductivity of LiF, providing a method to predict and correct experimental measurements under extreme conditions.

Contribution

It introduces a novel modeling approach that quantifies the impact of defects on LiF's thermal conductivity and extends to other solid materials with uncertainty estimates.

Findings

Defects significantly reduce LiF's thermal conductivity.

The model accurately predicts conductivity in defective LiF samples.

Methodology can be applied to various materials and defect types.

Abstract

Defect formation in LiF, which is used as an observation window in ramp and shock experi- ments, has significant effects on its transmission properties. Given the extreme conditions of the experiments it is hard to measure the change in transmission directly. Using molecular dynam- ics, we estimate the change in conductivity as a function of the concentration of likely point and extended defects using a Green-Kubo technique with careful treatment of size-effects. With this data, we form a model of the mean behavior and its estimated error; then, we use this model to predict the conductivity of a large sample of defective LiF resulting from a direct simulation of ramp compression as a demonstration of the accuracy of its predictions. Given estimates of defect densities in a LiF window used in an experiment, the model can be used to correct the observations of thermal energy through the window. In addition, the methodology we develop is extensible to modelling, with quantified uncertainty, the effects of a variety of defects on thermal conductivity of solid materials.