Density of alkali germanate glasses related to structure

The structural origin of the 'germanate anomaly' effect remains a matter of controversy. We employ in this study a quantitative description of the ger manate network structure to simulate the experimental density of potassium germanate glasses with K2O contents up to 40 mol%. The results show that th e short range order structure, including the change of germanium co-ordinat ion number from four to six, cannot reproduce the maximum in density. The ' germanate anomaly' effect seems to involve both short and medium range orde r structural changes as metal oxide is added to GeO2. (C) 2001 Elsevier Sci ence B.V. All rights reserved.