材料期刊网

We have investigated the structures, phonon dispersions, phase transitions and thermodynamics of Zr from first-principles calculations. At zero temperature, alpha-Zr transforms to omega-Zr at 0.98 GPa and then to beta-Zr at 31.6 GPa. The axial ratio c/a increases with increasing pressure for alpha-Zr, but it is nearly invariant under compression for omega-Zr. Within the quasi-harmonic Debye model, the full phase diagram of Zr was obtained. The zero pressure phase transition from alpha-Zr to beta-Zr occurs at 1130 K. The transition pressure from alpha-Zr to co-Zr at 300 K is 2.10 GPa and the predicted triple point is at 6.35 GPa, 910K, which is close to the experimental data. The thermal properties including the entropy, isotherm, isobar and thermal pressure in a wide range of pressure and temperature were predicted successfully. (C) 2010 Elsevier B.V. All rights reserved.