Investigation of structural, electronic and lattice dynamical properties of XNiH 3 (X ¼ Li, Na and K) perovskite type hydrides and their hydrogen storage applications Aysenur Gencer a,b , Gokhan Surucu a,c,d,* a Department of Physics, Middle East Technical University, Turkey b Department of Physics, Karamanoglu Mehmetbey University, Turkey c Department of Electric and Energy, Ahi Evran University, Turkey d Photonics Application and Research Center, Gazi University, Turkey article info Article history: Received 19 January 2019 Received in revised form 7 April 2019 Accepted 10 April 2019 Available online xxx Keywords: Hydrogen storage Perovskite type hydrides Mechanical properties Electronic properties Thermodynamic properties abstract XNiH 3 (X ¼ Li, Na, and K) perovskite type hydrides have been studied by using Density Functional Theory (DFT) and these materials are found to be stable and synthesizable. The X-ray diffraction patterns have been obtained and they indicate that all materials have the polycrystalline structure. The electronic properties have been investigated and it has been found that these structures show metallic character. The Bader partial charge analysis has also been performed. In addition, the elastic constants have been calculated and these materials are found to be mechanically stable. Using these elastic constants, the mechanical properties such as bulk modulus, shear modulus, Poisson's ratio have been obtained. Moreover, the Debye temperatures and thermal conductivities have been stud- ied. The anisotropic elastic properties have been visualized in three dimensions (3D) for Young's modulus, linear compressibility, shear modulus and Poisson's ratio as well as with the calculation of the anisotropic factors. Additionally, the dynamical stability has been investigated and obtained phonon dispersion curves show that these materials are dynamically stable. Also, the thermal properties including free energy, enthalpy, entropy and heat capacity have been studied. The hydrogen storage properties have been examined and the gravimetric hydrogen storage capacities have been calculated as 4.40 wt%, 3.57 wt % and 3.30 wt% for LiNiH 3 , NaNiH 3 and KNiH 3 , respectively. Furthermore, the hydrogen desorption temperatures have been obtained as 446.3 K, 419.5 K and 367.5 K for LiNiH 3 , NaNiH 3 and KNiH 3 , respectively. © 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved. * Corresponding author. Ahi Evran University, Department of Electric and Energy, 40100, Kirsehir, Turkey. E-mail address: g_surucu@yahoo.com (G. Surucu). Available online at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy xxx (xxxx) xxx https://doi.org/10.1016/j.ijhydene.2019.04.097 0360-3199/© 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved. Please cite this article as: Gencer A, Surucu G, Investigation of structural, electronic and lattice dynamical properties of XNiH 3 (X ¼ Li, Na and K) perovskite type hydrides and their hydrogen storage applications, International Journal of Hydrogen Energy, https://doi.org/ 10.1016/j.ijhydene.2019.04.097