Dynamics in a nonfragile glass-forming liquid

The dynamics of Na0.5Li0.5PO3 (T-g = 515 K, T-m = 749 K) a non fragile glass forming liquid has been investigated over a large temperature range (300 - 1000 K) and in a wide energy window using various experimental techniques. The susceptibility spectra obtained by coherent neutron scattering and depolarized light scattering between 1 and 10(4) GHz show mainly two contributions: a low frequency vibrational peak, the so-called Boson peak and a quasielastic component, referred to the beta(fast) process in the mode coupling theory (MCT). The data are discussed in relation to the mode coupling theory for the liquid glass transition. In particular, the temperature evolution of the susceptibility height in the beta(fast) region is compatible with a crossover temperature T-c similar to 620 K which is also deduced from a power law temperature dependence of the structural relaxation timescale, As a secondary beta(slow) process' observed by P-31 NMR, decouples from the structural relaxation timessale also below 600 K, a real change in the dynamics seems to occur around T-c similar to 620 K = 1.2 T-g in this non fragile glass forming liquid.