In Situ Raman Spectroscopy and DFT Studies of the Li₂GeO₃ Melt Structure.

Area of Science:

• Materials Science
• Solid-State Chemistry
• Spectroscopy

Background:

• Understanding the molecular structure of melts is crucial for predicting their properties.
• Lithium germanate (Li2GeO3) is a material with potential applications where melt properties are important.

Purpose of the Study:

• To elucidate the molecular-level structure of Li2GeO3 melt.
• To correlate the melt structure with its observed physicochemical properties, such as viscosity.

Main Methods:

• In situ Raman spectroscopy was used to observe the crystal-to-melt transformation.
• Factor group analysis was applied to interpret lattice phonons.
• Density functional theory (DFT) calculations were employed to model melt structures and assign spectral bands.

Main Results:

• Two characteristic Raman bands were identified: a mid-frequency band (495 cm-1) attributed to Ge-O-Ge bending and a high-frequency band (814 cm-1) to O-Ge-O stretching.
• Melting caused an anomalous blue shift in the bending band and a normal red shift in the stretching band.
• DFT calculations favored a chain-like [GeO2Ø2]n structure over a ring structure for the Li2GeO3 melt.
• The anomalous shift of the bending band was linked to the shrinkage of the [GeO2Ø2]n chain.

Conclusions:

• The Li2GeO3 melt structure is predominantly chain-like ([GeO2Ø2]n).
• This chain-like structure explains the high viscosity and crystal growth phenomena observed in Li2GeO3.
• The study provides fundamental insights into the structure-property relationships of molten germanates.