First-principles studies of defects, mechanical properties and electronic structure of Cr-based Laves phases

First-principles calculations have been performed to investigate the defects, mechanical properties and electronic structure of MCr2 (M = Nb, Ti and Zr) Laves phases. The results show that the ternary additive of V preferentially substitutes the Cr site and Zr the Nb site in NbCr2. W has a weak site preference on the Cr site in NbCr2. The ternary site substitutions are related to the electronic structure of NbCr2. Further calculations of the densities of states and charge density distribution of TiCr2 show that a strong covalent bonding between the small atoms (Cr) along the Kagome net forms a tetrahedral electronic network, which is a common feature for the electronic structure in Laves phases. Mechanical properties, such as elastic constants, elastic moduli and stacking fault energies of ZrCr2, were calculated additionally. The intrinsic and extrinsic stacking fault energies of ZrCr2 are found to be 112 mJ m(-2) and 98 mJ m(-2), respectively. (c) 2006 Elsevier Ltd. All rights reserved.