Dynamics and thermodynamics of molecular systems in the
vicinity
of the boundary between thermodynamically nonequilibrium glassy and
metastable supercooled liquid states are still incompletely explored
and their theoretical and simulation models are imperfect despite
many previous efforts. Among them, the role of total system entropy,
configurational entropy, and excess entropy in the temperature–pressure
or temperature–density dependence of global molecular dynamics
(MD) timescale relevant to the glass transition is an essential topic
intensively studied for over half of a century. By exploiting a well-known
simple ellipsoidal model recently successfully applied to simulate
the supercooled liquid state and the glass transition, we gain a new
insight into the different views on the relationship between entropy
and relaxation dynamics of glass formers, showing the molecular grounds
for the entropy scaling of global MD timescale. Our simulations in
the anisotropic model of supercooled liquid, which involves only translational
and rotational degrees of freedom, give evidence that the total system
entropy is sufficient to scale global MD timescale. It complies with
the scaling effect on relaxation dynamics exerted by the configurational
entropy defined as the total entropy diminished by vibrational contributions,
which was earlier discovered for measurement data collected near the
glass transition. Moreover, we argue that such a scaling behavior
is not possible to achieve by using the excess entropy that is in
excess of the ideal gas entropy, which is contrary to the results
earlier suggested within the framework of simple isotropic models
of supercooled liquids. Thus, our findings also warn against an excessive
reliance on isotropic models in theoretical interpretations of molecular
phenomena, despite their simplicity and popularity, because they may
reflect improperly various physicochemical properties of glass formers.