This experiment will examine the pressure and temeprature phase diagram of the elpasolite perovskite La2NiMnO6. The sample will be studied in the pressure range of 0-9 GPa at termpatres from 120-1200 K. It will examine the P-T regions of stability of the two knbwon phases of La2NiMnO6 and also look for new pahses in the high pressure temperature regime. If new phases are discovered it is hoped to either recover them metastably or mimick the phases observed by chemicl tuning. In a test experiment the phase diagram has roughl;y been mapped out in the 0-4 GPa region from 120-400 K. Where a monoclinic to rhombohedral phase transition is observed it is hoped to map this transition more accuralty and look for possible higher symmetry phases at high pressur and temperature.