Compass II calculated charges for ammonium nitrate are way out when compared with experimentally calculated charges, especially for the nitrate ion. I am trying to simulate supersaturated aqueous solution of ammonium nitrate with Forcite plus (MS 8), and MD results in a system, which contracts to much higher density (NPT dynamics) and the NVE dynamics results in hole formation, when force field charges are used in the simulation.Can experimental charges for ammonium nitrate be used with Compass II?