Pressure-driven modification of optoelectronic features of ACaCl3 (A = Cs, Tl) for device applications.

Intending to advance the use of halide-perovskites in technological applications, in this research, we investigate the structural, electronic, optical, and mechanical behavior of metal-halide perovskites ACaCl3 (A = Cs, Tl) through first-principle analysis and assess their potential applications. Due to the applied hydrostatic pressure, the interaction between constituent atoms increases, thereby causing the lattice parameter to decrease. The band structure reveals that band gap nature transits from indirect to direct at elevated pressure. Moreover, at high pressure, the electronic band structure shows a notable band gap contraction from the insulator (>5.0 eV) to the semiconductor region, which makes them promising for electronic applications. The charge density map explores the ionic and covalent characteristics of Cs/Tl-Cl and Ca-Cl under pressured and unpressurized environments. Induced pressure enhances the optical conductivity as well as the optical absorption that moves toward the low-energy region (red shift), making ACaCl3 (A = Cs, Tl) advantageous for optoelectronic applications. Additionally, this study reveals that the mechanical properties of ductility and anisotropy were found to be improved at higher pressures than in ambient conditions. Overall, this study will shed light on the technological applications of lead-free halide perovskites in extreme pressure conditions.

Exploration of the physical properties of the newly synthesized kagome superconductor LaIr3Ga2 using different exchange-correlation functionals.

LaIr3Ga2 is a kagome superconductor with a superconducting temperature (Tc) of 5.16 K. Here, we present the physical properties of the LaIr3Ga2 kagome superconductor computed via the DFT method wherein six different exchange-correlation functionals were used. The lattice parameters obtained using different functionals are reasonable, with a slight variation compared to experimental values. The bonding nature was explored. The elastic constants (Cij), moduli (B, G, Y), and Vickers hardness (Hv) were computed to disclose the mechanical behavior. The Hv values were estimated to be 2.56-3.16 GPa using various exchange-correlation functionals, indicating the softness of the kagome material. The Pugh ratio, Poisson's ratio, and Cauchy pressure revealed the ductile nature. In addition, mechanical stability was ensured based on the estimated elastic constants. The anisotropic mechanical behavior was confirmed via different anisotropic indices. The Debye temperature (ΘD), melting temperature (Tm), and minimum thermal conductivity (kmin) were calculated to characterize the thermal properties and predict the potential of LaIr3Ga2 as a thermal barrier coating material. The electronic density of states was investigated in detail. The McMillan equation was used to estimate Tc, and the electron-phonon coupling constant (λ) was calculated to explore the superconducting nature. The important optical constants were also calculated to explore its possible optoelectronic applications. The values of reflectivity in the IR-visible region are about 62% to 80%, indicating that the compound under study is suitable as a coating to reduce solar heating. The obtained parameters were compared with previously reported parameters, where available.

Justification of crystal stability and origin of transport properties in ternary half-Heusler ScPtBi.

In this study, the mechanical stability, machinability, flexibility, ductility, hardness and crystal stability have been analysed for the justification of suitability of ScPtBi for practical applications and device fabrication. We observed that ScPtBi satisfies the Born stability criterion nicely as well as possessing a negative value of formation enthalpy which suggests that ScPtBi is a mechanically stable compound and can be synthesized by chemical synthesis techniques. We have investigated the nature of the bonding in ScPtBi via Mulliken bond population analysis and charge density mapping which suggest that both ionic and covalent bonding exist in the ScPtBi with bonding and anti-bonding features. We have correlated band structure (BS), density of states (DOS), Fermi surface (FS) and charge density mapping to explain the origin of transport properties in ScPtBi by exploring the electronic behavior in detail with the help of first principles calculation. We have observed an octahedral hole like sheet due to a heavy hole pocket at the Γ point whose flat surfaces enhance transport properties in the direction parallel to the edges. The electron and hole like multi sheets achieved in the same topology are favorable for skipping of carriers and Fermi surface nesting. We have also calculated the electronic specific heat coefficient successfully using the density of states at the Fermi level.