  Alpha S8 is the most stable crystalline form, at ambient pressure and
temperature (STP), of elemental sulfur. In this paper we analyze the zero
pressure low temperature part of the phase diagram of this crystal, in order to
test a simple and flexible model molecule. The calculations consist in a series
of molecular dynamics (MD) simulations, performed in the constant pressure-
constant temperature ensemble. Our calculations show that this model, that
gives good results for three crystalline phases at STP and T>~300 K, fails at
low temperatures, predicting a structural phase transition at 200 K where there
should be none.
