Effects of doping on crystal and grain boundary in human enamel

In this paper, by use of the tight binding recursion method, the effects of doping on the electronic structure and the energy of grain boundary in hyd roxyapatite (OHAP) are investigated. Some important energetic information, such as structural energy of atom, interatomic energy and grain boundary en ergy are calculated. The results show that the crystal structure of OHAP wi ll be stabilized by the substitution of F for OH, and the substitution of C O3 for PO4 may result in deficiency of Ca. Doping Na, Mg, Sr, Ba, Ca or Pb into the grain boundary will lower the grain boundary energy. The grain bou ndary energy will be influenced from doping sensitively, such as Na, Mg, Sr , Ba, Ca or Pb. Especially, the grain boundary energy will be lowered drama tically by doping with Pb. (C) 2001 Elsevier Science B.V. All rights reserv ed.