On the role played by electrons in the stress-strain curves of ideal crystalline solids

TL;DR

This paper investigates how the electronic charge distribution in crystalline solids like copper, aluminum, and diamond influences their stress-strain behavior, revealing phase transition-like features driven by electronic effects.

Contribution

It introduces a thermodynamic approach using density functional theory to analyze electronic responses in stress-strain curves of crystalline solids, highlighting electronic effects beyond atomic displacements.

Findings

Stress-strain curves deviate from linear elasticity due to electronic effects.

Features of the curves can be interpreted as phase transitions related to electronic density of states.

Electronic charge redistribution influences mechanical properties and deformation mechanisms.

Abstract

The mechanical properties of a solid, which relate its deformation to external applied forces, are key factors in enabling or disabling the use of an otherwise optimal material in any application, strongly influencing also its service lifetime. Intrinsic crystal deformation mechanisms, investigated experimentally on single crystals with low dislocation densities, have been studied theoretically through atomistic simulations, mainly focusing on lattice-induced instabilities. Here, instead, we employ density functional theory and a thermodynamic analysis to probe and analyze the way in which the electronic charge of crystalline solids (Cu, Al and diamond) responds to uniaxial strain and affects their mechanical properties. Indeed, despite the very simple nature of our models, and in the presence of minimal atomic displacements, we find that the stress strain curves of Cu and Al deviate from a simple linear elastic behavior. Within a thermodynamics perspective, the features of such curves can be interpreted in terms of first and second order phase transitions, which originate from Van-Hove singularities of the electronic density of states crossing the Fermi level and electron redistribution within the solid, respectively.