FIRST-PRINCIPLES INVESTIGATION OF 7% CU-DOPED SRTIO₃ USING MATERIAL STUDIO: STRUCTURAL, ELECTRONIC, AND OPTICAL PROPERTIES

Abstract

Perovskite strontium titanate, SrTiO₃, attracts particular attention due to its wide bandgap, excellent dielectric properties, and great thermal stability, promising excellent application prospects in photocatalysis, optoelectronics, and solar energy conversion devices. However, the intrinsic SrTiO₃ presents limited absorption of visible light as a result of the large band gap (~3.2 eV), restricting its realization in solar‑driven applications [1], [2]. The transition metal doping is one of the active ways to enhance the optical absorption and tune electronic structure. Below, we report a detailed first‑principles investigation of the structural, electronic, and optical properties for Cu‑doped SrTiO₃ with 7 mol% copper substitution, using material models created and analyzed in BIOVIA Materials Studio. Finally, the doped system was modeled by replacing the sites of titanium (Ti) with the atoms of copper (Cu) within a 2 × 2 × 2 supercell of SrTiO₃ to obtain approximately 7 mol% doping. The geometry optimization and calculations of the electronic structure were done within the GGA of the PBE functional, with the addition of Hubbard U corrections (GGA + U) toward the proper description of the strongly correlated Cu 3d states [3], [4]. The obtained values for the structural parameter were compared with experimental lattice constants for undoped SrTiO₃, which resulted in good agreement, thus allowing us to validate the computational setup [5].The crystal structure showed that Cu doping leads to small lattice distortion due to the difference between the ionic radii of Cu²⁺ (0.73 Å) and Ti⁴⁺ (0.605 Å), because of which the doped lattice got expanded with an enlarged lattice constant and modified bond lengths for both Sr–O and Ti–O. In fact, the optimized lattice parameters showed increased cell volume relative to pristine SrTiO₃, consistent with earlier theoretical and experimental reports on transition metal dopants [6]. Importantly, the Cu dopant location and its local coordination environment influenced the symmetry of the perovskite lattice, leading to subtle octahedral tilting and a reduction in space group symmetry compared to the ideal cubic structure.