Electronic structure studies of bismuth compounds using high energy resolution X-ray spectroscopy and ab initio calculations

Highlights: • High energy resolution x-ray absorption spectroscopy for Bi compounds has been performed. • Experimental results are in good agreement with ab initio calculations. • Resolved pre-edge spectral feature indicates strong p-d orbital mixing. • Mixing with ligand orbitals has been also detected. Bismuth-based compounds are widely used as superconductors, catalysts and materials for optical devices. Their properties, and the possibility of controlling these properties, are determined by their electronic structure and the local environment of the Bi-centres. Although X-ray spectroscopy is a powerful method for revealing crystal and electronic structure, the results obtained so far have been limited by the energy resolution of the experimental data. Here, for the first time, we report X-ray absorption near edge structure (XANES) data, recorded in high energy resolution fluorescence detection (HERFD) mode at the Bi L_III and L_I edges for a number of bismuth compounds. Experimental data are analysed using ab initio calculations based on a finite difference method (FDMNES) code, for metallic Bi, Bi₂O₃, BiPO₄, Bi₄(GeO₄)₃ and NaBiO₃ compounds. It was observed that both the oxidation state and the length of the Bi-ligand bonds determine the exact position of the absorption edge, and this is in good agreement with other studies. Additionally, due to the high energy resolution, spectral features corresponding to strong Bi p-d orbital mixing were resolved. The results obtained here can be used as input for further investigations of the electronic structure of bismuth compounds in different chemical states.