Structural, elastic, and electronic properties of new 211 MAX phase Nb _2GeC from first-principles calculations

摘要

Very recently (2012, Phys. Rev Lett., 109, 035502) a new hexagonal (s.g. P63/mmc, #194) ternary phase Nb_2GeC, which belongs to so-called 211-like MAX phases, was discovered. In order to get a systematic insight into the structural, elastic, and electronic properties of Nb2GeC, we used two complementary DFT-based first-principles approaches (as implemented in the VASP and Wien2k packages) to calculate the optimized structural parameters, band structure, densities of state, Fermi surface, and a set of elastic parameters: elastic constants (C_(ij)), bulk modulus (B), compressibility (β), shear modulus (G), Young's modulus (Y), and elastic anisotropy indexes, which were discussed in comparison with available data. Besides, the inter-atomic bonding picture for Nb_2GeC was discussed using electron density maps and Bader's charge analysis.