Аннотации:
Crystal field parameters for two nonequivalent positions Ca (I) and Ca (II) for hydroxy-apatite (HAp) crystals from the density functional theory (DFT) are calculated. Calculations are compared with the experimental electron paramagnetic resonance (EPR) spectra (registered at two microwave frequencies) for the synthesized Mn-HAp powders Ca9.995Mn0.005(PO4)6(OH)2. It is found that in the investigated species, the manganese is redistributed between both calcium sites with prevalence in Ca (I). Agreement between the calculated and experimental data proves that crystal field parameters in HAp can be calculated in the classical DFT model using the distributed electron density.