α and β -tricalcium phosphate: A density functional study
Physical Review B 68, 205205 - 8 (2003)
α and β -tricalcium phosphate: A density functional study
Biologically important α- and β-tricalcium phosphates (TCPs) have been investigated using ab initio density functional calculations. α- and β-TCP have particularly large unit cells amounting to 312 and 273 atoms, respectively. The relationship between α-TCP and its three subcells, as well as the influence of the distribution of the Ca vacancies apparently existing in β-TCP have been studied. The calculated structural parameters for all the TCP phases, are in substantial agreement with experiment. The Ca-O distance varies continuously, while the P-O bonds distribute over a very narrow range. Oxygens hold the majority of the bonding electrons which reflects the ionic nature of the α and β phases. The results suggest that β-TCP is more stable than the α phase, and that β-TCP with uniformly distributed Ca vacancies is the most stable structure. The three 1/3 α-TCP subcells relax to similar structures, and we found that the full α-TCP cell and its subcells have very similar stability, electronic and structural properties, suggesting that the subcell can be a good approximation for studying α-TCP.
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- http://dx.doi.org/10.1103/PhysRevB.68.205205