Ab initio study of MgSiO 3 C2/c enstatite

摘要: We have used a newly developed ab initio constant-pressure molecular dynamics with variable cell shape technique to investigate the zero temperature behaviour of high pressure clinoenstatite (MgSiO3-C2/c) from 0 up 30 GPa. The optimum structure at 8 GPa, as well structural trends under pressure, compare very experimental data. At this we find noticeable “fluctuations” in chain configuration which suggests is on verge mechanical instability. Two distinct compressive behaviours then appear: one below and another above This phenomenon may be related observed transition lower symmetry P21/c phase involves reconfiguration silicate chains, that C2/c low pressures found here, an artifact dynamical algorithm preserves space group absence breaking fluctuations. Comparison calculations other magnesium phases, indicates size units (isolated and/or linked tetrahedra octahedra) are generally described by local density approximation; however, weaker linkages provided O-Mg-O bonds, not described. trend that, recently studied case H2O-ice, properties more inhomogeneous systems, like enstatite, improved using gradientcorrected functionals.