where n is the concentration of free charge carriers (electrons or holes) arising from the formation of charged point defects, e is the electronic charge, and ⇣ is the carrier mobility. ⇣ is estimated using a semi-empirical model with parameters that were fitted to experimentally measured room-temperature carrier mobilities. The model inputs, including bulk modulus and band effective mass, can be obtained from DFT calculations. ⇣ is estimated as