Following Steve's comment I actually tried configurations that should have
worked OK and did not. They include the perfect beta-cristobalite structure
and also an amorphous configuration that was minimized with another SiO2
Another thing is that I tried to run beta-cristobalite with a thermostat
for ~3-5 ps, and even using velocity rescaling every step, there was a
temperature spike which filled the crystal with defects and turned it
nearly to an amorphous.
I was wandering if someone could actually spot any problems with the input
file or the format of the data file. Any help/suggestions are welcomed.
Thanks in advance.