Mineralogical Society of Poland awarded Bartek Puzio with prestigeous prize for THE BEST PhD THESIS IN MINERALOGY, PETROLOGY AND GEOCHEMISTRY OF 2024.
Congratulations Bartek, the prize is well deserved. Your thesis “New method for prediction of thermodynamic functions for apatites” is outstanding. In this study, experimental data were collected on thermodynamic state functions (TFS) and molar volume for phosphate, arsenate and vanadate apatites containing Ca, Sr, Ba, Pb and Cd in the Me2+ cationic position and F, OH, Cl, Br and I in the X halide position. Based on the accumulated experimental data, a new method for predicting thermodynamic state functions was proposed for apatites. It was shown that the apatite supergroup is divided into distinct subgroups (populations) formed by Me10(AO4)6X2 with the same Me2+ cations and AO43- anions, but with different substitutions at the X position. Linear relationships between TFS and different physicochemical parameters of the element at the X position within the subgroups studied were observed and investigated. The method presented here for predicting molar volume Vm, enthalpy of formation from elements ΔH°f,el and standard entropy S° is based on regression analysis of linear relationships within subgroups between TFS and, for example, ionic radius of element X, lattice energy of apatite, or ΔH°f,el of their anions AO43- or X–. This made it possible to predict new TFS values for apatite and for previously unknown synthetic materials with apatite structure. The precision of the prediction is comparable to experimental uncertainties obtained using calorimetric measurements or dissolution experiments. The proposed prediction method can be applied to a wider range of apatite chemical compositions than other methods used to date. Using the predicted data, the author calculated other useful TFS, such as the Gibbs free energy of formation from elements ΔG°f,el and the solubility constant Ksp for the phases studied. Based on the updated TFS database for the apatite supergroup, it was possible for the first time to discuss trends in variability within and between subgroups. The results of this work open many new research directions, such as the experimental search for new compounds or testing the presented method on other groups of minerals.
