Tight-binding computations of elastic anisotropy of Fe, Xe, and Si under compression

A tight-binding total-energy model parametrized to first-principles linearized augmented plane-wave computations is applied to study elasticity and elastic anisotropy in Fe, Xe, and Si at high pressures. We find that the model works well in reproducing the compression, electronic structure, phase relations, and elasticity in these diverse materials. In Xe, for example, the same parametrization works well over a fivefold compression range from a van der Waals solid to a dense metal. We find that the cubic close-packed structures are all more anisotropic than hexagonal close packed and that at high pressures the elastic anisotropy approaches that of any central force nearest-neighbor model. We find that long-range, nonorthogonal parametrizations are necessary for greatest accuracy.