Phys. Scr. 98 (2023) 115976 https://doi.org/10.1088/1402-4896/ad03c6 PAPER Structural, mechanical and thermodynamic stability of the CaIn intermetallic compound for promising hydrogen storage: ab-initio calculations Khadidja Missoum , Saïd Meskine , Abdelkader Boukortt, Ahlam Benaouad and Nabila Mehtougui Laboratoire d’Elaboration et Caractérisation Physico Mécanique et Métallurgique des Matériaux (ECP3M), Abdelhamid Ibn Badis University of Mostaganem, Route Nationale N°11, Kharouba, 27000 Mostaganem, Algeria E-mail: khadidja.missoum.etu@univ-mosta.dz Keywords: DFT, binary intermetallic compound, CaIn, structural stability, phonon dispersion, mechanical properties, thermodynamic properties Abstract This study was conducted to investigate the structural, elastic, dynamical, mechanical, and thermodynamic properties of the binary intermetallic compound CaIn in various crystallographic phases, utilizing density functional theory (DFT) calculations. The results reveal that the compound is chemically and mechanically stable, as indicated by the formation energy, stability in the phonon dispersion, and elastic constants calculation. The mechanical and thermodynamic properties of our studied compound are only examined in the most stable calculated phase, which is the orthorhombic phase (Pmma). By calculating Pugh’s ratio / BG, it has been determined that this compound possesses a brittle character. The quasi-harmonic Debye (QHD) model was employed to analyze various thermodynamic parameters such as Debye temperature, volume variation, isothermal bulk modulus, heat capacity, and thermal expansion coefficient. These findings are expected to encourage further theoretical and experimental studies on the CaIn intermetallic compound for potential applications as a hydrogen storage material and in various other fields. 1. Introduction In recent years, researchers have been diligently working to create new materials with improved properties and performance for various applications. Intermetallic compounds are one such class of materials that have proven to be highly important to those of ordinary metals in practical applications due to their unique characteristics, such as their high melting points, high tensile strength, good stiffness, low density, high corrosion and oxidation resistance at elevated temperatures, and the potential they offer for a variety of purposes [1–7]. Research into intermetallics is focused on understanding their physicochemical and mechanical properties, as these determine the material’s suitability for specific uses ranging from aerospace engineering to medical implants. The tremendous potential offered by this group of materials has led research teams around the world to continue exploring its possibilities; thus far, promising results have been achieved that could revolutionize many industries in time [8]. One of the most important applications of intermetallic compounds is hydrogen storage. Hydrogen can be stored in intermetallic compounds, such as AB-type, AB 2 -type and AB 5 -type compounds; some intermetallics that have been studied include magnesium hydrides (MgH 2 )[9], TiFe, NaAl and LaNi 5 [10, 11], where it can be safely and securely stored in a solid-state form. This makes intermetallic compounds an ideal solution for hydrogen storage, as they are able to absorb large amounts of hydrogen at relatively low pressures. In addition, intermetallic compounds can be tailored to meet specific requirements, such as improved hydrogen storage capacity, improved hydrogen release rates, or improved stability. All of these advantages make intermetallic compounds an attractive option for hydrogen storage [12]. For this purpose, we are interested in the binary intermetallic CaIn compound. RECEIVED 12 May 2023 REVISED 29 September 2023 ACCEPTED FOR PUBLICATION 16 October 2023 PUBLISHED 27 October 2023 © 2023 IOP Publishing Ltd