title: On the structure of biomedical silver-doped phosphate-based glasses from molecular dynamics simulations.
abstract: First-principles and classical molecular dynamics simulations of undoped and silver-doped phosphate-based glasses with 50 mol% P2O5, 0-20 mol% Ag2O, and varying amounts of Na2O and CaO have been carried out. Ag occupies a distorted local coordination with a mean Ag-O bond length of 2.5 Å and an ill-defined first coordination shell. This environment is shown to be distorted octahedral/trigonal bipyramidal. Ag-O coordination numbers of 5.42 and 5.54-5.71 are calculated for first-principles and classical methodologies respectively. A disproportionation in the medium-range phosphorus Q(n) distribution is explicitly displayed upon silver-doping via CaO substitution, approximating 2Q(2)→Q(1) + Q(3), but not on silver-doping via Na2O substitution. An accompanying increase in FWHM of the phosphorus to bridging oxygen partial pair-correlation function is strong evidence for a bulk structural mechanism associated with decreased dissolution rates with increased silver content. Experimentally, Ag2O ↔ Na2O substitution is known to decrease dissolution and we show this to be a result of Ag's local bonding.
authors: Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ, UK. n.h.deleeuw@ucl.ac.uk.
authors: Richard I
authors: RI
authors: Ainsworth
authors: Jamieson K
authors: JK
authors: Christie
authors: Nora H
authors: NH
authors: de Leeuw
mesh_terms: D005139:Eyeglasses; D056004:Molecular Dynamics Simulation; D015394:Molecular Structure; D010710:Phosphates / Q000737:chemistry*; D012834:Silver / Q000737:chemistry*
chemical_list: D010710:Phosphates; D012834:Silver