Vibrational densities of states from molecular-dynamics calculations

A method for calculating the vibrational densities of states of crystalline materials by use of molecular dynamics (MD) is presented. It consists mainly of starting the calculation with all atoms at rest in their equilibrium positions, except one which is given an initial velocity; the time evolution of this velocity is Fourier transformed to give the local vibrational density of states, and the procedure repeated for nonequivalent atoms in the lattice. It is shown with examples that the vibrational densities of states are unbiased and show very low noise and that calculations with this method require much fewer MD steps than those performed using standard random initializations.