📝 SummarXiv

Abstract

Elastic constants are central material properties, frequently reported in experimental and theoretical studies. While their computation is straightforward in the absence of thermal fluctuations, finite--temperature methods often suffer from poor signal--to--noise ratios or the presence of strong anharmonic effects. Here, we show how to compute elastic constants in thermal ordered and disordered systems by generalizing a noise--cancellation method originally developed for piezoelectric coupling coefficients. A slight strain is applied to an equilibrated solid. Simulations of both the strained and unstrained (or oppositely strained) reference systems are performed using identical thermostatting schemes. As demonstrated theoretically and with generic one--dimensional models, this allows stress differences to be evaluated and elastic constants to be determined with much reduced thermal noise. We then apply this approach across a diverse set of systems, spanning crystalline argon, ordered silicon as well as amorphous silicon, poly(methyl methacrylate), and cellulose derivatives.