Search for: [Abstract = "Molecular mechanics simulations have been performed to undertake a systematic investigation into the structure and mechanical properties of α\-cristobalite undergoing uniaxial loading along each of the 3 mutually orthogonal principal directions and also hydrostatic pressure loading. Simulations were performed using both the BKS and Burchart force\-fields. The simulations indicate that pressure loading and uniaxial loading along the x3 direction leads to uniform variation of the four independent Si\-O\-Si intertetrahedral angles, indicativ of cooperative tetrahedral rotation about tetrahedr l axes which transform the α\-cristobalite structure into the 'idealised' β\-cristobalite structure. Uniaxial loading along either of the transverse directions \(x1 and x2\) leads to a divergence of the intertetrahedral angles, consistent with tetrahedral rotation about the tetrahedral axes which transform the idealised β\-cristobalite structure into the 'ordered' β\-cristobalite structure. The data also indicate that a phase transi ion to one of the proposed β phases may be induced by a negative hydrostatic pressure or tensile stress along x3. The phase transition is accompanied by a change in sign of some of the Poisson's ratios \(i.e. from positive to negative\). A negative hydrostatic pressure is also predicted to lead to conversion of initially positive to negative Poisson's ratio values \(within the same phase\)."]
