An ab initio Study on the Mechanical Stability, Spin-Dependent Electronic Properties, Molecular Orbital Predictions, and Optical Features of Antiperovskite A3InN (A = Co, Ni).

Structural, mechanical, spin-dependent electronic, magnetic, and optical properties of antiperovskite nitrides A3InN (A = Co, Ni) along with molecular orbital diagram are investigated here by using an ab initio density functional theory (DFT). The mechanical stability, deformation, damage tolerance and ductile nature of A3InN are confirmed from elastic calculations. Different mechanical anisotropy factors are also discussed in detail. The spin dependent electronic properties such as the band structure and density of states (DOS) of A3InN are studied and, the dispersion curves and DOS at Fermi level are different for up and down spins only in case of Co3InN. These calculations also suggest that Co3InN and Ni3InN behave as ferromagnetic and nonmagnetic, respectively. The induced total magnetic moment of Co3InN is found 2.735 µB/cell in our calculation. Mulliken bond population analysis shows that the atomic bonds of A3InN are contributed by both ionic and covalent bonds. Molecular orbital diagrams of A3InN antiperovskites are proposed by analyzing orbital projected band structures. The formation of a molecular orbital energy diagram for Co3InN is similar to Ni3InN with respect to hybridization and orbital sequencing. However, the orbital positions with respect to the Fermi level (E F) and separations between them are different. The Fermi surface of A3InN is composed of multiple nonspherical electron and hole type sheets in which Co3InN displays a spin-dependent Fermi surface. The various ground-state optical functions such as real and imaginary parts of the dielectric constant, optical conductivity, reflectivity, refractive index, absorption coefficient, and loss function of A3InN are studied with implications. The reflectivity spectra reveal that A3InN reflects >45% of incident electromagnetic radiations in both the visible and ultraviolet region, which is an ideal feature of coating material for avoiding solar heating.

Evaluation of the Thermoelectric Properties and Thermal Conductivity of CH3NH3PbI3-x Cl x Thin Films Prepared by Chemical Routes.

The thermoelectric properties and thermal conductivity of mixed-phase CH3NH3PbI3-x Cl x thin films have been reported as a function of temperature, ranging from room temperature (RT) to 388 K. Thermoelectric study confirms that CH3NH3PbI3-x Cl x is a p-type material and the charge carrier transport in CH3NH3PbI3-x Cl x is governed by polarons and the thermal scattering process. The Peltier function and power factor are found to decrease initially up to ∼325 K, after which they increase with increasing temperature. The position of (E F - E V) of all samples drops down sharply to zero level around 325 K. The avalanches of thermoelectric properties at ∼325 K indicate the existence of tetragonal-cubic phase transition in CH3NH3PbI3-x Cl x . The calculated thermal conductivity is very low, as desired for thermoelectric materials, due to strong anharmonic interactions. Both the figure of merit (ZT) and device efficiency increase with increasing temperature. However, ZT remains small with temperature. Despite the limitations on the operating temperature range due to phase complexity and small ZT, CH3NH3PbI3-x Cl x exhibits reasonable thermoelectric power and low thermal conductivity. This signifies the possibility of CH3NH3PbI3-x Cl x as a prospective thermoelectric material.