Dear All,
I'm trying to rebuild a monoclinic mineral crystal to a orthorhomic mineral crystal. My original monoclinic crystal was forcefield typed, then I rebuilt the crystal to orthorhomic. I tried different sapce groups, but I couldn't find one with which I can built proper bonds with the original forcefield type. So I changed the forcefield typing strategy, however, with this new strategy, I couldn't perform geometry optimization nor dynamic, the crystal structure became disordered. 
Does anyone have an idea why this happened? Should I change the size of the unit cell? 
Any suggestion would be appreciated!

Regards,
Jing