At a fixed temperature, the left-hand-side of Equation ( ) decreases monotonically with E F , crossing from positive to negative values at an equilibrium value of the Fermi energy E eq F . The charge neutrality condition is therefore satisfied by a unique E eq F , which is determined self-consistently from Equations ( )-( ). The hole and electron concentrations are then determined as p E eq F , T and n E eq F , T , respectively. It is important to distinguish T syn and T , which are used to calculate the concentration of defects in Equation ( ) and the carrier concentrations in Equations ( )-(12) in the system, respectively. In the charge neutrality condition, both temperatures must be specified to determine the free carrier concentrations. The distinction arises from the assumption that the concentration of defects in the system are fixed at the annealing temperature (T syn ), whereas the concentrations of free carriers are allowed to re-equilibrate to the measurement temperature (T ). The assumption stems from the fact that most defects are kinetically immo- bile and are therefore "frozen-in" at the synthesis temperature, though exchanges between different charge states of the same defect are possible. Accordingly, a VTAnDeM user has the freedom to specify T syn under the defect formation energy diagram (Figure ). However, the user need not specify T syn , in which case VTAnDeM will default to setting T syn = T . The latter applies to situations where defect concentrations are not fixed but can equilibrate to the measurement temperature, such as when mass transport and exchange with reservoirs is possible.