Work

The series of works is dedicated to establishing the basic laws of electronic and atomic structures formations and physical properties of functional calcium and cadmium apatite-like compounds. Using the state-of-the-art first-principles methods of calculations with the combination of various spectral techniques electronic, atomic structures and physical properties of apatite compounds with isomorphic substitution in cation and anion sublattices were studied. The changes of electron energy structure formation and interatomic chemical bonds of isomorphically-substituted with isovalent scheme in the cationic and anionic sublattices were established. The modifications in atomic environments and interatomic bonds lengths with different types of isomorphic substitution were investigated. The changes of valence band structures and atomic charge states by substitution in calcium hydroxyapatite calcium cations for cadmium ones, phosphate groups for vanadate or arsenatе ones and hydroxyl groups for fluorine, chlorine and bromine anions were established and analyzed. The elastic, piezoelectric tensors, dielectric constants, Born effective charges and phonon density of states of a wide range of calcium- and cadmium-based apatite-like compounds were calculated using density functional perturbation theory. The speed of sound in calcium phosphate fluoro-, chloro- bromoapatites was found to be larger along the sixth-fold screw axis than in the plane that is perpendicular to it. This conclusion should be used by the application of apatite as artificial bone and explain the orientation of human bone along the six-fold axis. The results obtained in the series of works have both fundamental and practical importance because they significantly stimulate the expansion of the scope of apatite-like structures applications, in particular, as a sorbent matrix for radioactive waste, disposal and storage of environmentally harmful matters and promote the development of synthesis methods of materials with desired properties.