Advances in the study of the deformation mechanism of stishovite

Stishovite, a mineral which is estimated to be abundant in the Earth's mantle, exhibits negative Poisson's ratios for a range of loading directions at specific ambient pressure ranges. Here, we investigate the deformation mechanisms which lead to auxetic behaviour in the (001) plane in further detail, and show that the two-dimensional projection of the structure is auxetic by the type α dilating rhombi mechanism. This corroborates the distorting octahedra three-dimensional mechanism described previously [Azzopardi et al., RSC Adv. 5, 8974 (2015)].