Atomistic origin of germanate anomaly in GeO2 and Na-germanate glasses: insights from two-dimensional 17O NMR and quantum chemical calculations

Sung Keun Lee; Bum Han Lee

doi:10.1021/jp063847b

Atomistic origin of germanate anomaly in GeO2 and Na-germanate glasses: insights from two-dimensional 17O NMR and quantum chemical calculations

J Phys Chem B. 2006 Aug 24;110(33):16408-12. doi: 10.1021/jp063847b.

Authors

Sung Keun Lee¹, Bum Han Lee

Affiliation

¹ Laboratory of Physics and Chemistry of Earth Materials, School of Earth and Environmental Sciences, Seoul National University, Seoul 151-742, Korea. sungklee@snu.ac.kr

PMID: 16913771
DOI: 10.1021/jp063847b

Abstract

The prominent problem in archetypal germanate glasses is the germanate anomaly where the density exhibits maxima at 15-20 mol % of the alkali oxide content. Here we report (17)O two-dimensional NMR spectra for GeO(2) and Na-germanate glasses where the presence of both bridging oxygen linking ([4])Ge and highly coordinated Ge (([5,6])Ge-O-([4])Ge) and nonbridging oxygen, and an increase in topological disorder are demonstrated at the density maximum, manifesting atomic origins of the anomaly. These densification mechanisms in germanate glasses with Na content are remarkably similar to densification in v-B(2)O(3) with pressure.