MOLECULAR-DYNAMICS STUDY OF THE GLASS-TRANSITION IN NI80P20

A detailed molecular-dynamics investigation of the liquid-glass transition is carried out for a realistic model of the metal-metalloid glass-former Ni80P20, with a view to assessing some of the predictions of the recent mode-coupling theory. This theory suggests that relaxation in glasses proceeds in two steps: fast relaxation at short times, corresponding to local atomic rearrangements and described by a power law, and slow relaxation at long times, corresponding to atomic transport (i.e. diffusion) and described by a stretched exponential (Kohlrausch law). The latter essentially disappears at the transition when the liquid becomes "structurally arrested", i.e. glassy. The transition is therefore characterized by the passage from a state of ergodicity (the liquid) to a state of non-ergodicity (the glass). Our simulations agree with the results of mode-coupling theory for the existence of two scaling regimes, but do not lead to critical exponents consistent with the predicted behaviour.