Properties of the Al-Si solid solution: Dynamical properties of the silicon substitutional and the aluminum vacancy

Using ab initio total-energy and molecular dynamics based on local orbitals and density-functional theory, we present results on the nonequilibrium Al-Si solid solution. We report on relaxations, vibrational spectrum, and superconducting transition temperature. Our results are in excellent agreement with experimental measurements on rapidly quenched samples which show evidence of lattice instabilities induced by the solute. We perform a similar analysis on the vibrational properties of the Al vacancy and discuss the results in terms of the mechanical instability leading to the crystalline-to-amorphous transition.