An integrated computational and experimental method for predicting hydrogen plateau pressures of TiFe1-xMx-based room temperature hydrides

Abstract

First-principles density functional theory (DFT) calculations were performed to investigate the effect of ternary alloying on the hydrogenation properties of the TiFe system. Al, Be, Co, Cr, Cu, Mn and Ni were selected as substitutional elements for Fe sites, in the light of their reported enhancement of activation, kinetic and thermodynamic properties. The use of special quasi-random structures to account for disordering of solute elements in the sub-lattice allowed a quantitative assessment of substitutional effects on the hydrogenation behaviour of single-phase TiFe1-xMx alloys, up to a solute concentration as high as 40 at.%. The energy of monohydride formation obtained by DFT calculations, approximated to the enthalpy of formation, was discussed in terms of changes in lattice parameter and hence plateau pressure. Based on the consistency between DFT calculations and earlier experimental results, a linear relationship between monohydride formation energy/enthalpy and plateau pressure was proposed as a simple method to predict the value of one of these physical properties from the other. The obtained correlation could therefore turn out to be a helpful tool to predict the ab/desorption plateau pressure of unexplored vast multi-component systems from DFT calculation, or, the other way around, could allow to estimate the formation enthalpy from only one pressure-composition-isotherm (PCI) measurement hence without the need of Van't Hoff plot.