The Fire algorithm (GOMethod = fire) assumes that all degrees of freedom
are comparable. All the velocities should be on the same
scale, which for heteronuclear systems can be roughly
achieved by setting all the atom masses equal, to the value
specified by this variable.
By default the mass of a proton is selected (1 amu).
However, a selection of GOFireMass = 0.01 can, in manys systems,
speed up the geometry optimization procedure.
If GOFireMass <= 0, the masses of each
species will be used.