Models of the Impurity Nitrogen Centers in Octacalcium Phosphate from the Density Functional Theory Calculations

This article discusses the application of computational methods using density functional theory (DFT) to construct models of the nitrogen impurity center in octacalcium phosphate (OCP). The performed DFT calculations are compared with the electron paramagnetic resonance spectra (g-factor and the hyperfine interaction constant A). It is shown that in the apatite layer of OCP, a \(\hbox {NO}_3^{2-}\) ${\text{NO}}_3^{2-}$ center is formed, while in the hydrated layer, a \(\hbox {NO}_2^{2-}\) ${\text{NO}}_2^{2-}$ center is the most probable one.