ABSTRACT The thermodynamics of hydride formation is one of the most important properties of the metal-hydrogen system, and states its potential for further uptake. For this reason, much research is focused on the use of first principle calculations as a predictive tool in the study of hydride stability. In this paper, First-principles density functional calculations were performed to predict the effect of co-substitution in NiTiH, Ti by Mg and Zr (x = 0.125, 0.25 and 0.375), as well as Ni by Cu and Cr (y = 0.125). Structural, thermodynamic stability and electronic properties were investigated. The formation enthalpy when Ti is substituted either by Mg or Zr with respect to their content is calculated and compared to the host NiTiH; it is found that the hydride stability decreases as Mg content increases while it increases when Zr content increases. The substitution of Ni by Cu destabilises the hydride while the stability of the hydride is enhanced when Ni is substituted by Cr. The simultaneous substitution of Ti by Mg (x = 0.375) and Ni by Cu (y = 0.125), leads to considerable destabilisation and an increase in cell volume of the hydride. The corresponding Ni0.875Cu0.125Ti0.625Mg0.375 compound is identified with optimum characteristics among the considered compositions, thereby can be considered as potential material for hydrogen storage.

中文翻译：

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通过 (Zr,Mg) 共同取代 Ti 和 (Cr,Cu) 共同取代 NiTi 氢化物稳定性：第一性原理研究

摘要 氢化物形成的热力学是金属-氢系统最重要的特性之一，并说明了其进一步吸收的潜力。出于这个原因，许多研究都集中在使用第一性原理计算作为氢化物稳定性研究中的预测工具。在本文中，进行了第一性原理密度泛函计算以预测 NiTiH、Ti 由 Mg 和 Zr（x = 0.125、0.25 和 0.375）以及 Ni 由 Cu 和 Cr（y = 0.125）共同取代的影响）。研究了结构、热力学稳定性和电子性质。计算 Ti 被 Mg 或 Zr 取代时的生成焓，并与主体 NiTiH 进行比较；发现氢化物稳定性随着Mg含量的增加而降低，而随着Zr含量的增加而增加。Cu取代Ni使氢化物不稳定，而当Ni被Cr取代时氢化物的稳定性增强。Ti 被 Mg (x = 0.375) 和 Ni 被 Cu (y = 0.125) 同时取代，导致相当大的不稳定和氢化物电池体积的增加。相应的 Ni0.875Cu0.125Ti0.625Mg0.375 化合物在所考虑的成分中具有最佳特性，因此可被视为潜在的储氢材料。