A model for the Ge–O coordination in germanate glasses

A successful model for the composition-dependence of the coordination number in borate glasses has been adapted for germanate glasses. The predicted coordination number has then been compared with neutron diffraction results for caesium and sodium germanate glasses, which show strong evidence of a significant growth and decline in the coordination number as modifier is added to the glass. The comparison with the predictions of the model support an interpretation in which the predominant higher coordination of germanium is five-fold, not six-fold.