Partitioning of dopant cations between β-tricalcium phosphate and fluorapatite

Abstract Mixed crystalline phase composite ceramics offer the possibility of partitioning defect species between the phases as well as occupancy of specific sites within a given phase. Here we use atomic scale simulations to study the site preference of an extensive range of divalent and trivalent substitutional ions across the five cation sites in β -tricalcium phosphate ( β -TCP) and the two cations sites in fluorapatite (FAp). This study indicates that in β -TCP small dopant species occupy the smaller of the five cation sites and vice versa . Conversely, in FAp, small divalent species occupy the nominally larger Ca(1) site while larger cations occupy the Ca(2) site. Partition energies between the two phases indicate that divalent species strongly segregate to β -TCP as do Al 3+ and Ga 3+ , whereas all other (larger) trivalent ions exhibit little preference.