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 orb itals and density-functional theory, we present results on the nonequi librium Al-Si solid solution. We report on relaxations, vibrational sp ectrum, and superconducting transition temperature. Our results are in excellent agreement with experimental measurements on rapidly quenche d 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 ins tability leading to the crystalline-to-amorphous transition.