ИСТИНА

The study of minerals is one of the most important practical tasks of Mӧssbauer spectroscopy. Destinezite, Fe3+2(PO4)(SO4)(OH)·6H2O, is a relatively rare mineral. It is crystalline (triclinic P-1) analog of amorphous diadochite. Fe3+ occupies two crystallographic positions. Two different iron ions form a [Fe-O(H)-Fe] pair, in which both Fe-O distances are almost equal (195 pm). The selected sample of Czechian destinezite has an average composition (Fe3+1.97Al0.03)(PO4)0.99(SO4)1.08(OH)0.87·5.95H2O, which is very close to the nominal. It was identified by X-ray diffraction, FTIR, and Raman spectroscopies. Its room-temperature Mӧssbauer spectrum is presented below. Figure 1. Room-temperature Mossbauer spectrum of destinezite sample. It can be well fitted as one resolved asymmetric Lorentz doublet with RTISα-Fe =0.41(1)·mm·s−1, RTQS =0.21(1) mm·s−1, FWHML =0.32 mm·s−1, FWHMR =0.30 mm·s−1. There are no traces of divalent iron or magnetic phases even with a thick sample. Simulation of the spectrum by a pair of symmetrical doublets leads to a significant deterioration of the result. Using Voigtian does not improve the model. Line broadening cannot be described by the Gaussian contribution. Since the coordination polyhedra of iron are highly distorted, it is difficult to make assumptions about how the Mössbauer parameters of two different iron ions should differ.