  Experimental studies of the glassy slowdown in molecular liquids indicate
that the high-temperature activation energy $E_{\infty}$ of glass-forming
liquids is directly related to their glass transition temperature
$T_{\text{g}}$. To further investigate such a possible relation between high-
and low-temperature dynamics in glass-forming liquids, we analyze the glassy
dynamics of binary mixtures using molecular dynamics (MD) simulations. We
consider a binary mixture of charged Lennard-Jones particles and vary the
partial charges of the particles, and thus, the high-temperature activation
energy and the glass transition temperature of the system. Based on previous
results, we introduce a phenomenological model describing relaxation times over
the whole temperature regime from high temperatures to temperatures well inside
the supercooled regime. By investigating the dynamics of both particle species
on molecular and diffusive length scales along isochoric and isobaric pathways,
we find a quadratic charge dependence of both $E_{\infty}$ and $T_{\text{g}}$,
resulting in an approximately constant ratio of both quantities independent of
the underlying observable, the thermodynamic ensemble, and the particle
species, and this result is robust against the actual definition of
$T_{\text{g}}$. This generic relation between the activation energy and the
glass transition temperature indicates that high-temperature dynamics and the
glassy slowdown are related phenomena, and the knowledge of $E_{\infty}$ may
allow to approximately predict $T_{\text{g}}$.
