Phase stability and elastic properties of Tan+1AlCn (n = 1-3) at high pressure and elevated temperature

We have studied the electronic structure of Tan+1AlCn (space group P63/mmc,n = 1-3) under uniform compression from 0 to 60 GPa and at temperatures from 0 to 1500 K using ab initio calculations. These phases can be characterized by alternating layers of high and low electron density and are referred to as nanolaminates. At 0 K we observe similar compressibilities in both the a and c directions for all phases investigated. This is unusual for nanolaminates. Based on the density of states analysis, we propose that these similar compressibilities may be caused by an increase in Ta-Al and Ta-Ta bonding strength as well as a stronger long-range interaction between TaC-TaC layers. No evidence of a phase transition is observed as the pressure is increased to 60 GPa. However, as the temperature is increased to approximately 1000 K without applying pressure, a first-order phase transition occurs in Ta3AlC2. These results are relevant for applications of Tan+1AlCn at elevated temperature and pressure