Study of the Bandgap and Crystal Structure of Cu 4 TiSe 4 : Theory vs. Experiment.

Matyszczak, Grzegorz; Sutuła, Szymon; Jóźwik, Paweł; Krawczyk, Krzysztof; Woźniak, Krzysztof

The aim of this study was to investigate the crystal structure and bandgap of the emerging material Cu4TiSe4 using both theoretical and experimental methods. We synthesized the title compound via solid-state synthesis from elements. The occurrence of the single crystals of the Cu4TiSe4 compound was proven by X-ray diffraction and EDX investigations. The resolved crystal structure proves the one recently reported for this compound. Additionally, we utilized the Uspex evolutionary algorithm for the prediction of the crystal structure of the Cu4TiSe4 compound and to check for the presence of potential polymorphs. It turns out that Cu4TiSe4 may theoretically occur in three different crystal structures (space groups: I-42m (no. 121), R3m (no. 160), and P-43m (no. 215)), in which the rhombohedral phase has the lowest energy. The ab initio study of the bandgap of Cu4TiSe4 showed that it is indirect for each polymorphic structure and varies in the range of 1.23–1.26 eV, while experimental investigation revealed a direct transition of energy of 1.35 eV, thus showing the potential of this compound for solar cell applications. Theoretical calculations suggested that the rhombohedral phase of Cu4TiSe4 should exhibit a negative or relatively low (0.64 eV) bandgap.

CRYSTAL structure; COPPER; SPACE groups; EVOLUTIONARY algorithms; SOLAR cells; SINGLE crystals

Crystals (2073-4352), 2023, Vol 13, Issue 2, p331

2073-4352

Academic Journal

10.3390/cryst13020331