A new thermodynamic model for solid metals under elastic deformations

Abstract

We present a theoretical model of the free Helmholtz energy (F) for solid metals that incorporates three contributions: the elastic part through a local strain description, the vibrational energy within a quasi-harmonic Einstein model with volume-dependent cohesive energy, and the electronic contribution in the free electron gas setting. To get F, we introduce discrete approximations of the Helmholtz energy defined in cubic lattices and show their convergence to F by finite element methods. For homogeneous deformations, the obtained model is applied to derive an equation of state (EOS) which shows a very good agreement with experimental data. Moreover, compared to other known theoretical EOSs, the present model is highly stable under different estimations of its parameters.