Crystal structure and band gap studies of sodalite: experimental and calculated results

• It is first proposed that the existence of the angle of 51.8° formed by O–O lines and the structural details of hydrogen bond in sodalite.
• The experimental photon band gap should be in range of 4.5 eV to 4.7 eV, comparable to the calculated value of 4.17 eV.
• The localization band nearest to the Fermi level is contributed by the hydrogen bond.

In this paper, we investigated the crystal structural properties of sodalite sample by X-ray diffraction and the band gap studies by means of UV–Vis absorption spectroscopy, and compared with the calculated results using density functional theory. The results of X-ray diffraction suggests that the chemical formula should be Na8(AlSiO6)4(OH)2·2(H2O). The optimized lattice parameter is found to be larger 0.45% than experimental value and the calculations demonstrated the structural details of the hydrogen bond located in sodalite cage. The hydrogen bond formed by water molecule and hydroxyl is implied from charge distribution analysis. As the rotation angle of O–O lines in hydrogen bond is 51.8°, the structure should be of the lowest energy. The optical band gap is measured to be 4.5–4.7 eV experimentally, while, the calculated value is 4.16 eV which is attributed to the localized state below Fermi level formed by the hydrogen bonds. Our results are favorable for the understanding the role of sodalite in silicate mud and contribute to further disposals and treatments.