  The exponentially repulsive EXP pair potential defines a system of particles
in terms of which simple liquids' quasiuniversality may be explained [A. K.
Bacher et al., Nat. Commun. 5, 5424 (2014); J. C. Dyre, J. Phys. Condens.
Matter 28, 323001 (2016)]. This paper and its companion present a detailed
simulation study of the EXP system. Here we study how structure monitored via
the radial distribution function and dynamics monitored via the mean-square
displacement as a function of time evolve along the system's isotherms and
isochores. The focus is on the gas and liquid phases, which are distinguished
pragmatically by the absence or presence of a minimum in the radial
distribution function above its first maximum. An NVU-based proof of
quasiuniversality is presented, and quasiuniversality is illustrated by showing
that the structure of the Lennard-Jones system at four selected state points is
well approximated by those of EXP pair-potential systems with the same reduced
diffusion constant. The companion paper studies the EXP system's isomorphs,
focusing also on the gas and liquid phases.
