First-principles studies on structural and electronic properties of TaCr_2 Laves phase

摘要

The structural properties, elastic properties and electronic structures of TaCr_2 are investigated by first-principles calculations. Heats of formation are calculated and compared for the three Laves phases (C15, C14 and C36). It is found that the C15 phase is the ground-state structure with the lowest energy and the C36 phase is an intermediate state between C15 and C14. These three phases, however, are very close in energy, indicating low stacking fault energies in this system. For the ground-state C15, C14 and C36 phases, we calculate three elastic constants from which the shear and Young's moduli are obtained. It is found that these calculated moduli of C15 are smaller than the experimental values obtained from polycrystals. The structural stability increases in the order C36, C14 and C15, which is also well explained through the densities of states of these compounds.