MOLECULAR SIMULATION OF THERMAL-DESTRUCTI ON PROCESSES IN ALUMINOPHOSPHATES

The thermal destruction process oi AlPO4-5 and VPI-5 was investigated by using molecular dynamics and computer graphic methods. The mobility of atoms in AlPO4-5 was increased and the framework became unstable a s the temperature increased. Finally the framework transformed into an amorphous phase. During this process, bonds between Al and O were fre quently broken or formed, P-O bonds were, however, scarcely changed. T his indicates that the Al-O bond in the framework is weaker than the P -O bond. AlPO4-5 has only one T (T=Al or P) site, whereas three crysta llographically distinct T sites are located in VPI-5. Thus, we also in vestigated dynamic differences between Al atoms located in distinct T sites during the thermal destruction process of VPI-5. It was found th at Al-O bonds formed by Al atoms at the T1 site are most apt to be bro ken.