First-Principles Study of Different Polymorphs of Crystalline Zirconium Hydride

• Published in: Journal of physical chemistry. C 2010-12, Vol.114 (50), p.22361-22368
• Main Authors: Zhu, Weihua, Wang, Rongshan, Shu, Guogang, Wu, Ping, Xiao, Heming
• Format: Article
• Language: English
• Subjects: C: Energy Conversion and Storage
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/jp109185n

We present a detailed study on the electronic structure, mechanical properties, phase stability, and thermodynamic properties of four polymorphs of crystalline zirconium hydride by using density functional theory within the generalized gradient approximation. An analysis of electronic structure shows that the zirconium hydrides retain metallic bonding over the whole hydrogen composition range. The calculated mechanical properties indicate that ζ-Zr2H and γ-ZrH are ductile, while δ-ZrH1.5 and ε-ZrH2 are brittle compared with α-Zr. The hydrides change from ductile to brittle in the order of ζ-Zr2H, γ-ZrH, ε-ZrH2, and δ-ZrH1.5. The formation enthalpies are negative for the four hydrides at the ambient pressure indicating that they are thermodynamically stable. Only the δ phase is thermodynamically stable in the whole pressure range. As the temperature increases, the decomposition reactions of the four hydrides are more and more favorable thermodynamically. The δ phase is thermodynamically easier to decompose than the others in the whole temperature range.