Ground State Properties and Energy-Related Applications of Cs2CaXCl6 (X = Si, Ge) Double Halide Perovskites: A Novel DFT Study

This investigation applies first-principles DFT methods to examine the fundamental structural, electronic, optical, thermoelectric and mechanical traits of Cs 2 CaXCl 6 (X = Si, Ge) compounds, aiming to uncover their potential utility in advanced energy systems. The electron-ion interactions use the Wu–Cohen Generalized Gradient Approximation (WC-GGA) and the Tran–Blaha modified Becke–Johnson (TB-mBJ) potential. All investigated materials are structurally and thermodynamically stable, supported by their negative formation energies and Goldsmith’s criteria. Moreover, Cs 2 CaSiCl 6 and Cs 2 CaGeCl 6 compounds exhibit wide band gaps in the ultraviolet region, ranging from 3.147 to 4.498 eV, depending on the choice of functional (GGA-PBE or TB-mBJ). A comprehensive analysis of the optical parameters, such as complex refractive index, absorption coefficient, and reflectivity, was performed under photon excitation from 0 to 14 eV. These results highlight the potential of Cs 2 CaSiCl 6 and Cs 2 CaGeCl 6 for future optoelectronic and photovoltaic applications. The thermoelectric properties of Cs 2 CaXCl 6 (X = Si, Ge) double halide perovskites were computed using the BoltzTraP code, indicating a remarkable combination of high electrical conductivity and low lattice thermal conductivity, which results in a significant figure of merit and highlights their viability in thermoelectric technologies. The elastic properties of Cs 2 CaXCl 6 (X = Si, Ge) confirm their mechanical stability and ductile nature, while highlighting the pronounced anisotropy induced by Ge substitution. These results confirm that the double halide perovskites are promising candidates for multifunctional applications, including nano-electronics, optoelectronics, thermoelectrics, and photovoltaics. Supplementary Material File (figure 1.docx) - Download - 229.04 KB File (figure 2.docx) - Download - 251.97 KB File (figure 3.docx) - Download - 147.17 KB File (figure 4.docx) - Download - 129.55 KB File (figure 5.docx) - Download - 114.12 KB File (figure 6.docx) - Download - 166.40 KB File (figure 7.docx) - Download - 142.55 KB File (figure 8.docx) - Download - 204.97 KB File (figure 9.docx) - Download - 368.52 KB File (manuscript.docx) - Download - 59.27 KB File (table 1.docx) - Download - 14.80 KB File (table 2.docx) - Download - 12.27 KB File (table 3.docx) - Download - 12.70 KB Information & Authors Information Version history Peer review timeline Published Computational and Theoretical Chemistry Version of Record1 Jun 2026Published Copyright This work is licensed under a Non Exclusive No Reuse License.

Authors Metrics & Citations Metrics Article Usage 205views 101downloads Citations Download citation Battal G. Yalcin. Ground State Properties and Energy-Related Applications of Cs2CaXCl6 (X = Si, Ge) Double Halide Perovskites: A Novel DFT Study. Authorea. 06 September 2025. DOI: https://doi.org/10.22541/au.175713132.29153749/v1 DOI: https://doi.org/10.22541/au.175713132.29153749/v1 If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download. For more information or tips please see 'Downloading to a citation manager' in the Help menu.