First-principles calculations to investigate optical, phonon and electronic properties of quaternary sulfides SrRECuS3 (RE = La, Nd, Tm)

https://doi.org/10.1016/j.inoche.2024.112449

The structure and properties of three layered heterometallic quaternary sulfides SrLaCuS₃, SrNdCuS₃ and SrTmCuS₃ were studied for the first time using first-principles calculations in the stoichiometric and nonstoichiometric approximations. The applied DFT-based computations were performed using a hybrid functional with the contribution of nonlocal exchange in the Hartree-Fock formalism. It was revealed that the nonstoichiometry of SrLaCuS₃ and SrNdCuS₃ must be considered for modeling phonon spectra, elastic properties and band gaps. The wavenumbers and types of the Raman and “silent” modes at the Г-point were determined. From the analysis of displacement vectors, the degree of participation of ions in each mode was determined. The elastic constants and elastic moduli of the reported sulfides were calculated.