  By performing molecular dynamics simulations of binary Lennard-Jones systems
with three different potentials, we show that increase of anharmonicity and
capacity for intermolecular coupling of the potential is the cause of (i) the
increase of kinetic fragility and nonexponentiality in the liquid state, (ii)
the Tg-scaled temperature dependence of the nonergodicity parameter determined
by the vibrations at low temperatures in the glassy state. Naturally these
parameters correlate with each other, as observed experimentally by T. Scopigno
et al., Science 302, 849 (2003).
