Monte Carlo study of glassy order in two-dimensional Lennard-Jones systems

The presence of disordered states in quenched Lennard-Jones systems in two dimensions is investigated by use of Monte Carlo simulations. No glassy state is observed in the one-component Lennard-Jones system; for all the (N,V,T) ensembles studied, the quenched system evolves readily into the ordered solid. When the two-component Lennard-Jones fluid is quenched to a low temperature, depending on the ratios of the concentration NA/NB and ``sizes'' σAA/σBB, it may evolve into either a fairly well-ordered solid, a microcrystalline state, or a disordered solid which may or may not be glassy. The two-component glasses are highly disordered with well-localized particles and have the characteristic split-second peak in the partial pair distribution function gBB, which is found in scattering experiments for metallic glasses and previous three-dimensional computer simulations of glasses. The authors propose that these glasses are only metastable and the phase-separated ordered lattice is the ground state. There is no hexatic order in the two-dimensional glasses; they have only short-range bond orientational correlation.