  We calculate local potential energy minima (inherent structures) for a simple
model of orthoterphenyl (OTP), from computer simulations over a wide
temperature range. We show that the results are very sensitive to the system
size. We locate, from the temperature and size dependence of inherent structure
energies, a well defined cross-over temperature that corresponds to the
dynamical critical temperature predicted by mode coupling theory and in mean
field spin glass models. Comparing the known phase space structure of mean
field $p$-spin models and the present results for the OTP model, we find
evidence supporting the proposed similarity between glass-forming liquids and a
class of spin glass models.
