Structural, bonding, dynamical, and electronic properties of liquid silicon: An ab initio molecular-dynamics study

We report an extensive first-principles molecular-dynamics study of metallic liquid silicon. Our description of the local order is in excellent agreement with x-ray- and neutron-diffraction experiments. The difference in internal energy between the simulated liquid phase and the crystal agrees well with the experimental enthalpy of melting. Analysis of the valence-electronic- charge density shows persistence of some covalent bonds in the melt. These bonds give rise in the power spectrum of the system dynamics to a well-identifiable feature associated with stretching vibrations. Unlike the case in the crystal, in the liquid the covalent bonds are continuously forming and breaking in response to atomic motion. The majority of bonds are broken on average, leading to fast diffusion and to metallic behavior of the melt. The calculated electronic conductivity shows good agreement with available experimental data.