Structure of phosphate and iron-phosphate glasses by DFT calculations and FTIR/Raman spectroscopy

• DFT simulations of simple structural phosphate units and cluster build of them were conducted.
• Theoretical FTIR and Raman spectra of the phosphate and iron-phosphate clusters were obtained.
• Influence of iron on phosphate structural units was determined.
• Theoretical and experimental FTIR and Raman spectra of 63P2O5 - 37Fe2O3 were compared.
• Structural features of the glass were obtained.

Phosphate glasses are very promising materials from the application and fundamental point of view. Properties of the glasses are strongly related to the structure which may be modified by various glass constituents. In the paper density functional theory calculations of simple phosphate structural units, chains build of them and iron-phosphate clusters are presented. Influence of a position of the unit in the chain is described. Structural changes of the units due to formation of bonds between non-bridging oxygens and iron atoms in different coordinations are shown. The optimized clusters are used then to calculate theoretical Raman and Fourier transform infrared spectra. The calculated spectra are then compared to the experimental results for an iron-phosphate glass from the pyrophosphate stoichiometry region. Finally the structural features of the glass are described.