Structure and Raman spectra in cryolitic melts: simulations with an ab initio interaction potential

Area of Science:

• Computational materials science
• Physical chemistry
• Solid-state chemistry

Background:

• Cryolitic melts, such as sodium aluminum fluoride (Na3AlF6), are crucial in industrial processes.
• Understanding their structure and dynamics is essential for optimizing material properties.
• Raman spectroscopy provides insights into melt structure and vibrational modes.

Purpose of the Study:

• To calculate Raman spectra of cryolitic melts using molecular dynamics simulations.
• To validate a transferable polarizable ionic potential derived from ab initio calculations.
• To establish a link between spectroscopic data and the structural/dynamical properties of melts.

Main Methods:

• Molecular dynamics (MD) simulations were employed.
• A polarizable ionic potential was developed via force-fitting to ab initio electronic structure calculations.
• Simulated Raman spectra were compared with experimental data and results from empirical potentials.

Main Results:

• The ab initio derived potential accurately reproduced the structure and dynamics of crystalline cryolite.
• Simulated Raman spectra of melts showed good agreement with experimental observations across various compositions.
• The study identified relationships between spectral bands and vibrational modes of AlFn coordination complexes.

Conclusions:

• The developed computational approach effectively models cryolitic melts.
• This method bridges the gap between Raman spectroscopy, diffraction experiments, and theoretical calculations.
• Results provide insights into melt cross-linking and ion diffusion properties.