Giancarlo Della Ventura, Jean-Louis Robert, Frank C. Hawthorne; Characterization of OH-F short-range order in potassium-fluor-richterite by infrared spectroscopy in the OH-stretching region. The Canadian Mineralogist ; 36 (1): 181–185. doi:
The infrared spectrum of a sample of potassium-fluor-richterite (PFR) is compared with that of a synthetic "potassium-richterite" having a similar OH-F content. The PFR spectrum shows an additional absorption band with respect to the synthetic sample, and this is assigned to a configuration involving Tl 71Al. The spectra show that there is strong short-range order of OH in the structure of PFR, that involves coupling between H and (Si,Al) rings of tetrahedra in response to the bond-valence requirements on the bridging atoms of oxygen in Al-O-Si dimers of tetrahedra.