Dynamic properties of Ni, Cu, and Fe in the condensed state: The molecular dynamics method

The distribution function for the density of vibrational states and the velocity distribution function in the crystalline, liquid, and amorphous states of Ni, Cu, and Fe are studied by the molecular dynamics method. In the crystalline and amorphous states, the dynamic properties are qualitatively the same, while in the liquid state, additional low-energy excitations appear. These excitations may be treated as low-frequency resonant modes that arise because of the significant contribution of nonlinearity to the interaction potentials. In all the three states, the velocity distribution functions are found to be Maxwellian; that is, the systems are ergodic, although nonlinearity-related contributions to the interaction potentials are high and the liquid and amorphous states are disordered.