Calcium phosphate clusters

Abstract The potential energy surfaces associated with [Ca 3 (PO 4 ) 2 ] n clusters are analyzed in detail using ab initio calculations for n ranging from one to four. Considering separated clusters, energy criteria favor the so-called Posner's cluster Ca 9 (PO 4 ) 6 , which is the core of the actual structural model of amorphous calcium phosphate. This is rationalized through the existence of a distinct CaO bonding pattern in this cluster. Considering aggregated clusters as a possible model for amorphous calcium phosphate, the aggregation of Ca 3 (PO 4 ) 2 clusters appears as an alternative to Posner's hypothesis.