Quantitative Studies on Local Structure of Molten Binary Potassium Germanates

Four- and high-fold coordinated germaniumatmos (Ge-V and Ge-VI) exist in binary K2O-GeO2 melts. Four-fold coordinated germanium atomsoccupy a dominantposition in the melt and only four-fold coordinated exists in themelt when the K2O content exceeds a certain amount. Deconvolutionof the stretching vibrational bands of nonbridging oxygen of [GeO4] tetrahedra of Raman spectra by Gaussian functions was carriedout, and the quantitative distribution of different Q(n) species in molten binary potassium germanates wasobtained. In situ high temperature Raman spectraof xK(2)O-(100-x)GeO2,samples containing 0, 5, 11.11, 20, 25, 33.3, 40, and 50 %mol K2O, were measured. The structure units and a series of modelclusters have been designed, optimized, and calculated by quantumchemistry ab initio calculations. The computationalsimulation in conjunction with the experiments put forward a novelmethod to correct the experimental Raman spectra of the melts. Deconvolutionof the stretching vibrational bands of nonbridging oxygen of [GeO4] tetrahedra of Raman spectra by Gaussian functions was carriedout, and the quantitative distribution of different Q(n) species in molten binary potassium germanates wasobtained. The result on all molten samples show that four-fold coordinatedgermanium atoms occupy a dominant position in the melt and only four-foldcoordinated exists in the melt when the K2O content exceedsa certain amount. For melts with high GeO2 content, withthe increasing K2O content, the structure of [GeO4] tetrahedra gradually changes from a three-dimensional network consistingof both six-membered and three-membered rings to a three-dimensionalnetwork that presents all three-membered rings.

Automated summary

In binary K2O-GeO2 melts, both four-fold and high-fold coordinated germanium atoms exist, with four-fold coordination dominating in the melt when the K2O content exceeds a certain amount. The quantitative distribution of different Q(n) species in molten binary potassium germanates was obtained by deconvolution of the stretching vibrational bands of nonbridging oxygen of [GeO4] tetrahedra. Quantum chemistry ab initio calculations were used to design, optimize, and calculate the structure units and model clusters, which, in conjunction with experimental data, proposed a novel method to correct the experimental Raman spectra of the melts. The results revealed that four-fold coordinated germanium atoms occupy a dominant position in the melt, and the structure of [GeO4] tetrahedra gradually changes as the K2O content increases.