  Experiments and computer simulations of the transformations of amorphous ices
display different behavior depending on sample preparation methods, and on the
rates of change of temperature and pressure to which samples are subjected. In
addition to these factors, simulation results also depend strongly on the
chosen water model. Using computer simulations of the ST2 water model, we study
how the sharpness of the compression-induced transition from low-density
amorphous ice (LDA) to high-density amorphous ice (HDA) is influenced by the
preparation of LDA. By studying LDA samples prepared using widely different
procedures, we find that the sharpness of the LDA-to- HDA transformation is
correlated with the depth of the initial LDA sample in the potential energy
landscape (PEL), as characterized by the inherent structure energy. Our results
show that the complex phenomenology of the amorphous ices reported in
experiments and computer simulations can be understood and predicted in a
unified way from a knowledge of the PEL of the system.
