TIGHT-BINDING MOLECULAR-DYNAMICS SIMULATIONS OF THE VIBRATION PROPERTIES OF ALPHA-TITANIUM

Phonon thermal anomalies in alpha-titanium are studied by means of tig ht-binding microcanonical molecular dynamics simulations. The frequenc ies of the zone centre [0 0 0 1]LO and TO phonons, and the [0 0 0 1]TA phonon at q = 1/3 are determined at different temperatures via the po wer spectrum of the autocorrelation function associated with the corre sponding projections of atomic velocities. It is shown that even at ve ry low temperatures the effects of anharmonicity in vibrational proper ties are strong and dependent on both wave propagation direction and f requency. In particular, the frequencies of the TO and TA phonons are shown to decrease while the frequency of the [0 0 0 1]LO phonon increa ses with crystal temperature, in agreement with experiment. Copyright (C) 1998 Elsevier Science B.V.