Muskan Nabi

Chiral hybrid organic–inorganic perovskites offer a chemically tunable platform in which inversion-asymmetric crystal fields and strong spin–orbit coupling generate spin-split band edges, yet the mechanisms through which the chiral molecules and the inorganic framework interact to produce spin splitting are not well understood. Here we use the electronic chirality measure—a wave-function-based metric—to quantify molecular chirality across three substitution series of chiral metal halides derived from methylbenzylammonium ligands. We find that halogen functionalization increases the valenceband spin splitting from 6.6 meV in the parent system to 64.8 meV in the benzylic-halogenated (S-MBA)X series and up to 110.0 meV in the side-chain-halogenated (S-MBA)CH2X series (X = H, F, Cl, Br). In contrast, for the pnictogen-substituted (S-MBA)Y series (Y = P, As, Sb, Bi), the splitting remains in the few-meV regime. The electronic chirality measure captures changes in the chiral electronic structure and provides a useful molecular descriptor for comparison with parityviolating energy differences, but it does not alone determine the band-edge splitting. The largest splittings emerge when electronic chirality, intrinsic cation dipoles, and inorganicframework distortion act cooperatively. Within each series, larger intrinsic cation dipoles are associated with smaller spin splitting energies. Large band-edge splitting occurs only when molecular chirality is efficiently converted into the induced chiral Pb/I framework mode, as parametrized by chirality transfer efficiency (CTE), and combined with a favorable cation electrostatic environment.

Explorations of new stable lead free perovskites have currently achieved substantial interest in the field of photovoltaics and optoelectronics as it tries to overcome the instability issue and avoid toxicity related with the lead based perovskites. We herein not only comprehensively tried to explain the experimentally synthesized two inorganic halide double perovskite materials but exploring their broader structural stability and also provide us a guideline to better understand their possible potential applications. For this purpose we performed density functional theory to investigate the structural, electronic, optical, elastic and thermoelectric properties of these materials. The stability of these cubic materials is validated by optimizing the structure, from the tolerance factor, mechanical stability test. These materials are found to be small band gap semiconductors with outshining optoelectronic performance. Due to high optical absorption, high conductivity and low reflectivity they have great potential to be used as a light absorbing material for photovoltaic application. Because, of small band gap we also tried to explore the variation of various transport properties with chemical potential. The semiconducting nature of materials results in ZT close to unity predicting its excellent application in thermoelectric technology.

Ferromagnetic rare‐earth‐based inverse perovskites Gd₃AlX (X = B, N) are studied using hybrid functionals in the framework of density functional theory. Different exchange correlation potentials are employed to analyze the structural parameters and geometry of the materials. The spin polarization and band structure explain the metallic behavior of these materials with high values of magnetic moment. The calculated elastic constants specify all materials are ordered perovskite compounds, among which Gd₃GaB, Gd₃GaN, Gd₃InN are brittle in nature while as Gd₃InB is ductile in nature. The quasi‐harmonic Debye model was used to predict the thermodynamic properties of the material. The analysis of thermoelectric properties viz. Seebeck coefficient, electronic and thermal conductivities at higher temperature has been carried out. To check the optoelectronic response of the material various optical properties have been calculated up to 14 eV photon energy range. The competent thermoelectric and optoelectronic properties with high value of magnetic moment and ductile character suggests the application in thermoelectric and electro‐optic devices.

The state‐of‐the‐art density functional theory is used to investigate various properties of rare‐ earth based inverse perovskites Gd₃AlX (X = B, N). The materials show robust structural stability at high pressures without undergoing any phase transition. The ferromagnetic character is retained at high pressures with high value magnetic moments 7.09 μ_B and 7.38 μ_B at 0 GPa for Gd₃AlB and Gd₃AlN, respectively. In view of Poisson's and Pugh's ratio, the ductility and brittleness of Gd₃AlX (X = B, N) has been analyzed. The mechanical stability is maintained throughout the pressure range with high value of Debye temperature. Transport properties have been calculated at different pressures for both the alloys, which show excellent thermoelectric properties. Besides, this the variation on some significant thermodynamic properties is also studied. Our successful prediction of the stabilization of the metallic Gd₃AlX (X = B, N) has proposed a route to synthesize novel rare‐earth–based inverse perovskites.