Abstract
The structural features and macroscopic properties of binary Na2O-GeO2 melts at 1373 K were investigated by integrating in-situ high temperature Raman spectroscopy, classical molecular dynamics simulations, and quantum chemistry (QC) ab initio calculations. Theoretical simulations and experimental characterization show that the melts consist of [GeO4] tetrahedra with germanium atoms in four-fold coordination. As the Na2O content increases, the melts change in the [GeO4] tetrahedral network, resulting in the formation of smaller three-membered rings. A series of [GeO4] tetrahedral clusters has been designed, optimized, and calculated by QC ab initio calculations. In the computational simulation coupled with the experiment, we proposed a novel method to correct Raman spectra by compensating Raman scattering cross-sections influence, which allows precise quantification of Qi species distribution. On the basis of the obtained species distribution, a structure-dependent viscosity model was developed, which indicates that the relative contribution of Qi units to melt viscosity decreases in the sequence Q4 > Q3 > Q2 > Q1. These findings offer new insights into the structural evolution of binary Na2O-GeO2 melts and provide a robust framework for correlating local structural units with macroscopic viscosity. The study provide theoretical foundation for design and optimization of advanced functional materials.