An isothermal–isobaric computer simulation of the supercooled-liquid/glass transition region: Is the short-range order in the amorphous solid fcc?

[N,P,T] Monte Carlo simulations of metastable supercooled-liquid and amorphous phases of Lennard-Jones atoms indicate several distinct signatures for identifying the glass transition boundary; i.e., the density, enthalpy, and pair distribution function dependences on temperature and pressure are different for the two phases. The effective hard-sphere packing fraction ηa at the glass transition boundary is verified to be the same whether the glass is prepared by temperature quenching or pressure crushing. Using ηa and liquid-state perturbation theory, the glass transition boundary is calculated for the metastable pressure–temperature phase diagram of the Lennard-Jones system. Finally, we argue that the evolution of the PDF structure as a function of degree of metastability suggests that the amorphous phase is a ’’distorted fcc packing.’’ A comparison with experiment is made.