The monovacancy formation energy and its effect on the electronic property, the lattice parameters and the hardness of the new found MAX phase, Nb2GeC

The monovacancy formation energies of each element Nb, Ge and C in the MAX phase Nb2GeC are obtained by ab initio calculation in the present paper. It is noted that the vacancy of each element has a slight effect on the hybridization bonding. If there is a vacancy of either Ge or C, the hybridization bonding will be slightly reduced. However, if there is a Nb vacancy, the hybridization bonding will be increased between the d-orbital and p-orbital. In contrast, the vacancies can substantially reduce the conductivity of the MAX phase Nb2GeC. It is also noted that if there is a vacancy of either Ge or C, the hardness of the Nb2GeC decreases, while it is increased if there is a Nb vacancy.