  The Lennard-Jones 12-6 potential (LJ) is arguably the most widely used pair
potential in Molecular Simulations. In fact, it is so popular that the question
is rarely asked whether it is fit for purpose. In this paper, we argue that,
whilst the LJ potential was designed for noble gases such as argon, it is often
used for systems where it is not expected to be particularly realistic. Under
those circumstances, the disadvantages of the LJ potential become relevant:
most important among these is that in simulations the LJ potential is always
modified such that it has a finite range. More seriously, there is by now a
whole family of different potentials that are all called Lennard-Jones 12-6,
and that are all different - and that may have very different macroscopic
properties. In this paper, we consider alternatives to the LJ 12-6 potential
that could be employed under conditions where the LJ potential is only used as
a typical short-ranged potential with attraction. We construct a class of
potentials that are, in many respects LJ-like but that are by construction
finite ranged, vanishing quadratically at the cut-off distance, and that are
designed to be computationally cheap. Below, we present this potential and
report numerical data for its thermodynamic and transport properties, for the
most important cases: cut-off distance rc=2 (LJ-like) and rc=1.2 (a typical
colloidal potential).
