Ab-initio calculation of bulk and surface models of A- and B- tricalcium phosphate

alpha- and beta-tricalcium phosphate [Ca3(PO4) 2 TCP] are very important bioceramic materials in clinical studies because of their biocompatibility, bioactivity, osteoconductivity, and an ability to form a uniquely strong interface with bone tissue. As a preliminary step to elucidate the reason for these advantages, an ab initio calculation has been performed to study the electronic structure and mechanical properties of both TCP crystal polymorphs. Also studied are the surface structures created from the bulk models. The bulk crystal calculation results imply that both TCP polymorphs are large gap insulators with similar electronic structures. There is larger charge transfer existing in alpha-TCP than in beta-TCP. The calculated mechanical properties indicate that beta-TCP is somewhat softer than beta-TCP. The surface calculation indicates that the surfaces are positively charged overall. The detailed information enriches our understanding of the TCP polymorphs and might be useful in the future study.