On the structure of biomedical silver-doped phosphate-based glasses from molecular dynamics simulations

Phys Chem Chem Phys. 2014 Oct 21;16(39):21135-43. doi: 10.1039/c4cp00574k. Epub 2014 Jul 29.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Eyeglasses
  • Molecular Dynamics Simulation*
  • Molecular Structure
  • Phosphates / chemistry*
  • Silver / chemistry*

Substances

  • Phosphates
  • Silver