Structure Prediction And Study The Properties Of Zirconium Hydride By First Principles

Zirconium hydride?Zr-H?has a low neutron capture cross section,and is used as the common cladding material of neutron moderator and nuclear fuel rods in nuclear reactors.The new structures of zirconium hydrogen alloy are predicted in this paper,and the mechanical properties,thermodynamic properties and superconducting properties are investigated under different proportion using the first-principle method.In addition,the influences of hydrogen content on properties of zirconium hydrogen alloys are discussed.The main conclusions are as follows:1.Two new structures of P4₂/mmc ZrH and P6₃/mmc ZrH₃ are explored successfully.The calculated results of phonon spectrum,enthalpy and mechanical properties show that the P6₃/mmc ZrH₃ is a stable structure.However,P4₂/mmc ZrH is a metastable phase.The calculation results show that the shapes of phonon spectrum of Eliashberg and the phonon DOS are very similar,and the electron phonon coupling is uniformly distributed in the phonon frequency.All the vibration modes contribute to the electron-phonon coupling,and phonon modes lower than 5 THz frequency region has the main contribution to electron-phonon coupling,occupying about 50%of the total ?,and the phonon mode of Zr atoms plays a major role in the low frequency region.Through the McMillan equation,we obtain the superconducting transition temperature of 11.7 K of ZrH₃,and the superconducting transition temperature of the isotope ZrD₃ is about 9.21 K.2.The electronic structure,mechanical properties and thermodynamic properties of the five kinds of zirconium hydrides were systematically studied by the first principles method.The results show that the hydrides of zirconium are metallic.The interaction between Zr and H becomes stronger with the increase of the hydrogen.The analysis of the elastic constants shows that the zirconium hydride is anisotropic to the compression,and the hydrogen content is high,which makes the zirconium hydride brittle.The main contribution of the heat capacity comes from the acoustic mode of the lattice vibration at lower temperatures,while the optical mode of the lattice vibration?hydrogen vibrational contribution?has a greater contribution to the heat capacity at higher temperatures.