A force-field based analysis of the deformation mechanism in α-cristobalite

Abstract

α-cristobalite is a metastable polymorph of silica which has the remarkable property of exhibiting a negative Poisson's ratio (auxetic). In this study, the mechanical properties and deformation mechanisms of this system were investigated through a force-field based approach. Besides simulations on the actual structure of α-cristobalite, a number of simulations where the rigidity of SiO2 tetrahedra was increased, were also conducted. This was done in order to obtain a clearer picture of the role which these tetrahedra play in determining the mechanical properties of this system. These systems were loaded in an off-axis direction in a number of planes about the [001] direction and the deformations observed were compared with those of type II rotating rectangle systems. It was discovered that the mechanical properties of α-cristobalite can be accurately described through the semi-rigid version of this model, even for cases where the tetrahedra were fully rigid.