The local coordination around Ag cations in silver borate glasses has been studied by comparing their experimental x-ray absorption near edge spectra (XANES) at the Ag K edge with results of theoretical simulations. Different trial structural models have been tested using knowncrystallographic environments as starting points for further modifications. The effort has been concentrated on exploring which structural features and trends improve the agreement between simulated spectra and experiment. The XANES of borate glasses cannot be reproduced by any of the crystalline sites. In order to describe the general shape of the spectrum, about eight or more neighbouring atoms within a radial distance of similar to 3.0 Angstrom have to be included. The most plausible model is characterised by a first shell Ag-O bond distance of R=2.2-2.3 Angstrom, distributing randomly the remaining atoms at longer distances. The substitution of some next nearest neighbour oxygen atoms with boron improves the agreement with experimental spectra
Local structure around Ag cations in silver borate glasses studied by XANES.
2003
Abstract
The local coordination around Ag cations in silver borate glasses has been studied by comparing their experimental x-ray absorption near edge spectra (XANES) at the Ag K edge with results of theoretical simulations. Different trial structural models have been tested using knowncrystallographic environments as starting points for further modifications. The effort has been concentrated on exploring which structural features and trends improve the agreement between simulated spectra and experiment. The XANES of borate glasses cannot be reproduced by any of the crystalline sites. In order to describe the general shape of the spectrum, about eight or more neighbouring atoms within a radial distance of similar to 3.0 Angstrom have to be included. The most plausible model is characterised by a first shell Ag-O bond distance of R=2.2-2.3 Angstrom, distributing randomly the remaining atoms at longer distances. The substitution of some next nearest neighbour oxygen atoms with boron improves the agreement with experimental spectraI documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
