Mechanical properties and elastic constants of atomistic systems through the stress-fluctuation formalism
E Voyiatzis, COMPUTER PHYSICS COMMUNICATIONS, 184, 27-33 (2013).
A rigorous approach to computing the mechanical properties of solids is based on the stress-fluctuation formalism. The main advantages of this route are its applicability to both homogeneous and inhomogeneous systems and its fast convergence compared to strain-fluctuation based methods. However, its implementation has been hindered by the complexity of evaluating strain derivatives of many-body interactions such as the angle-bending and the torsional ones. In this study, its implementation in open-source software is presented. It utilizes recently-proposed analytical expressions by Van Workum et al. K. Van Workum, G. Gao, J.D. Schall, J.A. Harrison, J. Chem. Phys. 125 (2006) 144506 to compute strain derivatives of many-body interactions. Thus, their numerical evaluation, which induces numerical fluctuations in the computed quantities, is avoided. The mechanical properties and the elastic constants of long-chain atactic polystyrene are estimated. The convergence behavior of the Born and the stress correlation terms is investigated. The estimated elastic moduli are in good agreement with experimental data. (C) 2012 Elsevier B.V. All rights reserved.
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