I have a low temperature single crystal X-ray structure of a compound that exhibits a reversible phase change by DSC at 500K. I would like to investigate this phase change to see how the structure changes at high temperature. Is there a way to set the temperature of the cell when performing a geometry optimization or is there a better way to go about determining the new structure? Also, how do you set the temperature for which thermal ellipsoids are calculated in a PhononDOS calculation? I can only seem to get them calculated at 298K.