Ab initiocalculations of the thermodynamics and phase diagram of zirconium

Abstract

The finite-temperature density-functional theory and quasiharmonic lattice dynamics are used to calculate the Gibbs free energy and quasiharmonic phonons of the hexagonal-close-packed ͑hcp͒ and omega ͑͒ crystal structures for Zr. The hcp phonon dispersions agree with experiment; the phonon dispersions have not been measured yet. From the free energy, the volume thermal expansion coefficients of ␣-Zr are predicted. The calculated volume thermal expansion coefficients for ␣-Zr are in good agreement with the experiment data at T Ͼ 100 K. Our calculated results found that at zero-temperature the lowest-energy phase is not the but the hcp phase. This conclusion is in accordance with the result of Schnell and Albers, but in disagreement with those of Ahuja et al. and Jona and Marcus. The predicted phase boundary of ␣ → is in good agreement with the available experiment; however, other theoretical results are far from the experiment at high temperatures.

Ab Initio Enhanced calphad Modeling of Actinide-Rich Nuclear Fuels

“…This shows that our DFT-PAW calculation correctly reproduces experimental finding [37,38] that αZr is the most stable ground state phase at zero temperature and pressure, with total energy 96.485 J/mole lower than ωZr. This result also matches previous DFT calculations using both FPLMTO [39] and PAW [40]. However, previous calculations by Bajaj et al [41] found the energy of αZr to be about 1 kJ/mole higher than ωZr.…”

Density functional study of the phase diagram and thermodynamic properties of Zr

“…If one can obtain the free energies of different phases within quasi-harmonic approximation (QHA), the phase boundary can be calculated by comparing the difference of the free energies. In our previous work [20], we only obtained the phase boundary of a-and x-Zr within QHA.…”

Orientation Relations During theα-ωPhase Transition of Zirconium:In SituTexture Observations at High Pressure and Temperature

“…The electronic transfer between the broad sp band and the much narrower d band in group IV transition metals is a likely driving force behind structural transitions [9] and has stimulated a large number of molecular dynamic investigations that explore the changes in bonding [10][11][12][13].…”