Evaluation of mechanical properties and negative poisson's ratio behavior in crystalline SiO2 materials: An atomistic approach

Abstract

The structural changes with volume expansion in low-temperature (a) phases of quartz and cristobalite, the typical polymorphs of silicon dioxide (SiO 2), have been studied through first-principles calculations using the projector-augmented-wave (PAW) method, with particular emphasis on their negative Poisson's ratio behavior. The dominant mechanism of expansion is the increase of the Si-O-Si angles within their crystalline structures, whereas the SiO4 tetrahedron undergoes only a slight distortion. We provide theoretical ab initio results for a complete set of independent elastic constants of quartz and cristobalite with volume expansion. For comparison, the adiabatic elastic constants of both polymorphs are evaluated at finite temperatures, using the molecular-dynamics simulations with a nonempirical pairwise potential. Our calculated elastic properties are found to be in good agreement with the experimental data.