First-Principles Study of Different Polymorphs of Crystalline Zirconium Hydride

Abstract

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 -Zr 2 H and γ-ZrH are ductile, while δ-ZrH 1.5 and ε-ZrH 2 are brittle compared with R-Zr. The hydrides change from ductile to brittle in the order of -Zr 2 H, γ-ZrH, ε-ZrH 2 , and δ-ZrH 1.5 . 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.

Modeling of Some Physical Properties of Zirconium Alloys for Nuclear Applications in Support of UFD Campaign

“…First principles calculations of the equilibrium crystalline lattice parameters, free energy of formation at different temperatures, and the phonon density of states were discussed by Blomquist and by Zhu et al, [35,36]. A detailed overview of the problem of hydrogen solubility in Zr and its alloys was provided by Anghel [13].…”

Structure and Thermodynamical Properties of Zirconium Hydrides from First‐Principle

“…The atomic structure used today are from neutron experiments that dates back some 50 years and it is quite debatable whether one should trust them fully. A number of recent works have used ab-initio computational methods to try to improve the picture somewhat and several groups have used DFT calculations to present, for example, lattice constants and elastic properties for pure Zr as well as some of the known hydride polymorphs [8,9,10,11,12]. Domain et al used ultrasoft pseudo potentials (UPP) and plane-waves single electron wave functions together with a GGA exchange-correlation (xc) functional PW91 to compute the structural parameters of the hydrides, the H-solution energies in Zr, and αZr elastic coefficients [8].…”

“…Zhu's group presented in a recent study the structural as well as the elastic coefficient of the four ZrH x polymorphs also utilizing UPP and xc functional PW91. They, further, presented an analysis of the relative phase-stability w.r.t temperature for the various hydrides using phonon-calculations evaluated at the gamma-point only [11]. Zhang et al recently presented electronic structure calculation on -ZrH 2 using the projector-augmented wave (PAW) method together with xc-functional PBE [12].…”

“…There still exists some gaps and some cases where published elastic coefficients do not match from one group to another. Zhu et al recently published a list of elastic coefficient of the four ZrH x hydrides but did not note any other calculations made of these [11]. In…”

Formation and characterization of hydride blisters in Zircaloy-4 cladding tubes

“…First, the crystallographic Figure 11: (a) Nanohardness measurements with a 10mN load on two profiles on a 217 µm deep blister on the radial circumferential plane, (b) evolution of the hardness of the hydrided zirconium as a function of the hydrogen content from [31,66,67,68,69,70], (c) elastic modulus measured from the nanohardness measurements considering a ν=0.3 Poisson ratio and (d) evolution of the elastic modulus of the hydrided zirconium as a function of the hydrogen content from [31,65,68,71,72,73,74].…”