Microscopic property of Li impurity in biphasic calcium phosphate

Recently Li doping is employed to control the properties of bioceramic biphasic calcium phosphate (BCP), which consists of β - Ca 3 ( PO 4 ) 2 ( β -TCP) and hydroxyapatite(HAp). We investigated the microscopic properties of Li in BCP through first-principles electronic structure calculations. The stable microscopic structure of Li-driven state is identified by comparing the formation enthalpies of Li-driven structures: interstitial ( Li int ) and substitutional ( Li Ca ). It is found that the Li int is more stable than the substitutional state Li Ca . The Li int atom is strongly coupled to three or four O atoms, which stabilizes the interstitial state. The Li int is calculated to be relatively more stable in β -TCP than in HAp, because the electronic level of Li int is much lower in β -TCP than in HAp.