Using first‐principles calculations, the structural, elastic, and electronic properties of MoAlB have been investigated. The optimized lattice constants exhibit fair agreement with the experimental results. The computed elastic constants satisfy the mechanical stability conditions for MoAlB. The Mo‐based boride MoAlB is elastically anisotropic and classified as brittle material. This boride is expected to be thermally conductive due to its high Debye temperature of 693 K. The metallic conductivity of this compound is predicted by means of electronic structure calculations. The chemical bonding in MoAlB is basically covalent that is assured with the results of DOS, Mulliken population, and charge density distribution. The hardness value of 11.6 GPa for MoAlB suggests that it is relatively soft compared to many others borides. The Fermi surface is formed due to low dispersive Mo 4d‐like bands, which makes the compound a conductive one.

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The ground state physical properties of the newly synthesized 312 MAX compound, Hf 3 AlC 2 have been investigated using the first-principles density functional theory (DFT). The optimized unit cell parameters show good agreement with the experimental values. The calculated elastic constants and phonon dispersion confirm the mechanical and dynamical stabilities of this new compound. High bulk modulus, combined with low shear resistance and low Vickers hardness, indicates good machinability of Hf 3 AlC 2 , as expected for a metallic compound. On the other hand, significant stiffness due to large Young's modulus as well as the brittle nature according to the calculated Pugh's and Poison's ratios and Cauchy pressure are comparable to that of a ceramic. The present calculations show that Hf 3 AlC 2 is elastically and optically anisotropic. The chemical bonding in Hf 3 AlC 2 consists of a mixture of metallic, covalent and ionic contributions. The calculated Fermi surface contains quasi-twodimensional topology, which indicates possible superconductivity of Hf 3 AlC 2 . The new phase Hf 3 AlC 2 may also be a promising thermal barrier coating (TBC) material. The calculated enthalpy and entropy are found to increase with temperature above 100 K though a decrease is observed for the free energy.

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This document is the author's post-print version, incorporating any revisions agreed during the peer-review process. Some differences between the published version and this version may remain and you are advised to consult the published version if you wish to cite from it.

Metal halide perovskites have become more popular for applications in solar cells and optoelectronic devices. In this study, the structural, electronic, mechanical, and optical properties of lead and lead-free metal halide cubic perovskites CsPbBr3 and CsGeBr3 and their Ni-doped structures have been studied using the first-principle density functional theory. Ni-doped CsGeBr3 shows enhanced absorbance both in the visible and the ultraviolet region. The absorption edge of Ni-doped CsBBr3 (B = Pb, Ge) shifts toward the lower energy region compared to their undoped structures. Undoped and Ni-doped lead and lead-free halides are found to have a direct bandgap, mechanical stability, and ductility. A combined analysis of the electronic, mechanical, and optical properties of these compounds suggests that lead-free perovskite CsGe0.875Ni0.125Br3 is a more suitable candidate for solar cells and optoelectronic applications.

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