Chalcogenophosphate CsMnPS₈ as a Promising Semiconductor for Photonic, Thermoelectric, Radiation-Protection and...

Density functional theory (DFT) calculations were employed to investigate the structural, electronic, vibrational, optical, thermoelectric, photoluminescence, and radiation-shielding properties of CsMnPS₈. Structural optimization confirms the stability of the crystal, while the Birch-Murnaghan equation of state yields an equilibrium volume of 545.2 ų, a ground-state energy of - 61.45 eV/f.u., and a bulk modulus of 44.7 GPa, indicating moderate mechanical rigidity. The optimized framework comprises interconnected MnS₆ octahedra and PS₄ tetrahedra with Cs⁺ ions occupying the interlayer cavities. Electronic band-structure calculations predict a direct band-gap semiconductor, and the density of states reveals that Mn-3d and S-3p orbitals dominate the states near the valence- and conduction-band edges. The absence of imaginary phonon frequencies confirms the dynamical stability of the compound. Optical calculations indicate strong absorption in the ultraviolet region, accompanied by moderate reflectivity and favorable dielectric behavior, supporting its suitability for optoelectronic applications. Thermoelectric analysis demonstrates a high Seebeck coefficient together with tunable electrical conductivity, highlighting the potential for efficient energy-conversion devices. The calculated photoluminescence spectrum exhibits a strong emission peak in the 630-640 nm visible region. In addition, the calculated radiation-shielding parameters suggest efficient attenuation of low- and intermediate-energy photons. These results demonstrate that CsMnPS₈ is a stable multifunctional semiconductor with potential applications in optoelectronic, thermoelectric, photonic, and radiation-shielding technologies.