Comparison of Crystal Structure Between Carbonated Hydroxyapatite and Natural Bone Apatite with Theoretical Calculation

In this study, nanosized carbonated hydroxypatite and stoichiometric hydroypatite were synthesized. Chemical analyses, as well as infrared spectroscopy and X-ray diffraction, were applied to investigate the composition, structure and chemical groups of all the samples. Furthermore, the structure and the crystal energy of all samples were analyzed by software and the mathematic methods. The results show that when CO23 is added into the solution after the reaction, the carbonated hydroxyapatite samples and natural bone apatite are similar in crystal structure, composition and crystallite size. Chemical analyses suggest that natural bone apatite and all synthetic carbonated hydroxypatite samples have the same molecular formula. Meanwhile, the computed crystal energy indicates that the carbonated hydroxypatite type-B substitution has lower crystal energy and better stability. Moreover, the fitting FTIR spectra prove that there is more type-B substitution than type-A substitution in all samples.