title: Mechanism for negative poisson ratios over the alpha- beta transition of cristobalite, SiO2: A molecular-dynamics study
abstract: The adiabatic elastic constants ( C(ij)) of cristobalite have been evaluated successfully over the temperature range of 300-1800 K using the molecular-dynamics method with a fluctuation formula. Cristobalite shows a negative Poisson ratio over this temperature range. However, the mechanisms differ between the alpha and beta phases. In the cubic beta phase, C44 exhibits a value extremely close to C11 rather than C12, in contrast to the Cauchy relation. This predicts a remarkable property that the longitudinal and transverse velocities coincide for the acoustic waves propagating along the [100] direction.
authors.affiliation: Center for Promotion of Computational Science and Engineering, Japan Atomic Energy Research Institute, Tokyo, 153-0061, Japan.
authors.initials: H
authors.lastname: Kimizuka
authors.initials: H
authors.lastname: Kaburaki
authors.initials: Y
authors.lastname: Kogure