Crystallochemical analysis of the crystal structure of PbGa2S4: The bond valence model


Introduction. The crystal structure reported in the literature for the PbGa2S4 ternary sulphide has been determined by using the X-ray powder diffraction technique. Due to a quite low number of independent reflections observed for the X-ray powder diffraction pattern of PbGa2S4 (i.e. because of the low observations-to-parameters ratio), the atomic coordinates of the PbGa2S4 structural model have not been properly refined in the least-squares refinement procedure but have been merely taken from the analogous structure of the CaGa2S4 ternary sulphide
Purpose. In order to verify the structural model reported for the PbGa2S4 compound, this structure has been examined within the framework of the bond valence model. 
Methods. The structure of PbGa2S4 has been analyzed by using the bond valence model. For all symmetrically independent atoms in the reported crystal structure of PbGa2S4, the coordination shells have been determined and the bond valence sums have been calculated from the cation–anion bond lengths. 
Results. The values of the bond valence sums are found to be in fair numerical agreement with the expected oxidation states of the ions in the PbGa2S4 structure. 
Conclusion. The results of the bond valence analysis of PbGa2S4 clearly indicate the reasonable accuracy and reliability of the aforementioned structural model reported for the PbGa2S4 compound

Keywords: crystal structure, inorganic compounds, chalcogenides, complex sulphides, bond valence model