Density of states and the velocity autocorrelation function derived from quench studies

We show how, for a harmonic solid, the density of normal mode states and the velocity autocorrelation function can be found by analyzing the temperature of the solid after its kinetic energy has been abruptly quenched. In a molecular dynamics simulation of an interacting Lennard-Jones system we show what happens to these results as the solid is made anharmonic and how, in the liquid state, these techniques can be used to study the role of anharmonicity in the velocity autocorrelation function.