BaPd 2 As 2 belongs to 122 pnictide group, famous for exhibiting superconductivity at high temperatures and other electronic correlations. Unlike the 122 iron arsenides, BaPd 2 As 2 exhibits superconductivity at low temperature when realized in theThCr 2 Si 2 type structure (I4/mmm). We have performed density functional theory (DFT) based calculations to investigate the structural, elastic, electronic, thermodynamic, and optical properties of BaPd 2 As 2 in this study. The structural, elastic, and the band structure features are compared with the available experimental and theoretical results. Pressure and temperature dependences of various important thermodynamic functions, e.g., bulk modulus, specific heats at constant pressure and volume, coefficient of volume thermal expansion, and Debye temperature are studied in details for the first time. The optical parameters of BaPd 2 As 2 are also studied in details for the first time. The optical properties compliment the electronic band structure characteristics. Optical constants show significant dependence of the state of polarization of the incident electric field. BaPd 2 As 2 exhibits high reflectance in the infrared and near-visible region and strongly absorbs the ultraviolet radiation. The relevance of the electronic energy density of states and the characteristic phonon frequency to superconductivity in BaPd 2 As 2 is also discussed.

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We have investigated theoretical Vickers hardness, thermodynamic and optical properties of four zirconium metal-based MAX phases Zr 2 AC (A = Al , Si , P and S ) for the first time in addition to revisiting the structural, elastic and electronic properties. First-principles calculations are employed based on density functional theory (DFT) by means of the plane-wave pseudopotential method. The theoretical Vickers hardness has been estimated via the calculation of Mulliken bond populations and electronic density of states. The thermodynamic properties such as the temperature and pressure dependent bulk modulus, Debye temperature, specific heats and volume thermal expansion coefficient of all the compounds are derived from the quasi-harmonic Debye model. Further, the optical properties, e.g., dielectric functions, indices of refraction, absorption, energy loss function, reflectivity and optical conductivity of the nanolaminates have been calculated. The results are compared with available experiments and their various implications are discussed in detail. We have also shed light on the effect of different properties of Zr 2 AC as the A-group atom moves from Al to S across the periodic table.

This is the first DFT-based first-principles prediction of the detailed optical and thermodynamic properties, including Vickers hardness and Fermi surface of 211 MAX phase Ti 2 GeC for which superconductivity (T c~ 9.5 K) was reported very recently. The calculated structural properties are in excellent agreement with experiments. Our results on elastic parameters indicate a slight elastic anisotropy and brittleness of the compound. The chemical bonding is seen to be a combination of covalent, ionic and metallic nature. The rather stronger covalent bonding is responsible for its high Vickers hardness of 11.6 GPa. The investigated Fermi surface is formed mainly by the low-dispersive bands, which should be responsible for the presence of superconductivity in Ti 2 GeC. All the optical properties are evaluated and analyzed for two different polarization directions of incident photon. The temperature and pressure dependence of primitive cell volume, thermal expansion coefficient, specific heats, bulk modulus, and Debye temperature of Ti 2 GeC are derived from the quasi-harmonic Debye model with phononic effect and the various implications are discussed in details.

First-principles calculations within the density functional theory (DFT) with GGA-PBE exchangecorrelation scheme have been employed to predict the structural, the elastic and the electronic properties of newly discovered lithium silicide superconductor, Li 2 PtSi 3 , for the first time. All the theoretical results are compared with those calculated recently for isostructural Li 2 IrSi 3 . The present study sheds light on the effect of replacement of transition metal element Ir with Pt on different mechanical, electronic, and superconducting properties. The effect of spin-orbit coupling on electronic band structure was found to be insignificant for Li 2 PtSi 3 . The difference in superconducting transition temperatures of Li 2 PtSi 3 and Li 2 IrSi 3 arises primarily due to the difference in electronic energy density of states at the Fermi level. Somewhat reduced Debye temperature in Li 2 PtSi 3 plays a minor role. We have discussed the implications of the theoretical results in details in this study.

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