title: Paracrystalline Disorder from Phosphate Ion Orientation and Substitution in Synthetic Bone Mineral.
abstract: Hydroxyapatite is an inorganic mineral closely resembling the mineral phase in bone. However, as a biological mineral, it is highly disordered, and its composition and atomistic structure remain poorly understood. Here, synchrotron X-ray total scattering and pair distribution function analysis methods provide insight into the nature of atomistic disorder in a synthetic bone mineral analogue, chemically substituted hydroxyapatite. By varying the effective hydrolysis rate and/or carbonate concentration during growth of the mineral, compounds with varied degrees of paracrystallinity are prepared. From advanced simulations constrained by the experimental pair distribution function and density functional theory, the paracrystalline disorder prevalent in these materials appears to result from accommodation of carbonate in the lattice through random displacement of the phosphate groups. Though many substitution modalities are likely to occur in concert, the most predominant substitution places carbonate into the mirror plane of an ideal phosphate site. Understanding the mineralogical imperfections of a biologically analogous hydroxyapatite is important not only to potential bone grafting applications but also to biological mineralization processes themselves.
authors.affiliation: Department of Chemistry, Colorado State University , Fort Collins, Colorado 80523-1872, United States.
authors.forename: Mary E
authors.initials: ME
authors.lastname: Marisa
authors.affiliation: Department of Chemistry, University of Southern California , Los Angeles, California 90089-0105, United States.
authors.forename: Shiliang
authors.initials: S
authors.lastname: Zhou
authors.affiliation: Department of Chemistry, University of Southern California , Los Angeles, California 90089-0105, United States.
authors.forename: Brent C
authors.initials: BC
authors.lastname: Melot
authors.affiliation: Department of Chemistry, Hope College , Holland, Michigan 49423-3605, United States.
authors.forename: Graham F
authors.initials: GF
authors.lastname: Peaslee
authors.affiliation: Department of Chemistry, Colorado State University , Fort Collins, Colorado 80523-1872, United States.
authors.forename: James R
authors.initials: JR
authors.lastname: Neilson
mesh_terms: D001842:Bone and Bones / Q000737:chemistry*; D003460:Crystallization; D017886:Durapatite / Q000737:chemistry*; D008958:Models, Molecular; D010710:Phosphates / Q000737:chemistry*; D033362:Powder Diffraction; D017356:Synchrotrons
chemical_list: D010710:Phosphates; D017886:Durapatite