First-principles calculations of structural, elastic and electronic properties of (TaNb)0.67(HfZrTi)0.33 high-entropy alloy under high pressure

Abstract

To clarify the effect of pressure on a (TaNb) 0.67 (HfZrTi) 0.33 alloy composed of a solid solution with a single body-centered-cubic crystal structure, we used first-principles calculations to theoretically investigate the structural, elastic, and electronic properties of this alloy at different pressures. The results show that the calculated equilibrium lattice parameters are consistent with the experimental results, and that the normalized structural parameters of lattice constants and volume decrease whereas the total enthalpy difference ΔE and elastic constants increase with increasing pressure. The (TaNb) 0.67 (HfZrTi) 0.33 alloy exhibits mechanical stability at high pressures lower than 400 GPa. At high pressure, the bulk modulus B shows larger values than the shear modulus G, and the alloy exhibits an obvious anisotropic feature at pressures ranging from 30 to 70 GPa. Our analysis of the electronic structures reveals that the atomic orbitals are occupied by the electrons change due to the compression of the crystal lattices under the effect of high pressure, which results in a decrease in the total density of states and a wider electron energy level. This factor is favorable for zero resistance.

Effect of Hf Substitution on Mechanical Properties of TiNbTaZr Medium Entropy Alloy by First Principle Calculation

“…In general, harder materials have higher Young's modulus. [ 31 ] Therefore, TiNbTaHf has higher hardness and higher modulus.…”

“…To obtain the most stable crystal structure supercell model, all the supercell structure models of these four medium entropy alloys were geometrically optimized, and the stable structure with the lowest ground state energy was selected for research [ 31 ] according to the setting conditions of the above parameters. Symmetry operations are performed during optimization to maintain the positive BCC structure as an orthogonal structure.…”

“…In general, harder materials have higher Young's modulus. [31] Therefore, TiNbTaHf has higher hardness and higher modulus. In Table 6, there is a Ti─Nb anti-bond with an overlap population of −0.33 in TiNbTaZr, and the population of the remaining bonds is >0, which belongs to the mixed state of ionic bonds and covalent bonds, so the alloy has good ductility.…”