Transport coefficients in silicate melts from structural data via a structure-thermodynamics-dynamics relationship

Area of Science:

• Geochemistry
• Materials Science
• Computational Chemistry

Background:

• Experimental determination of silicate melt transport properties (viscosity, diffusivities) under extreme conditions is challenging.
• Transport coefficients are highly sensitive to melt composition, complicating estimations and extrapolations.
• Understanding these properties is crucial for geological processes and materials applications.

Purpose of the Study:

• To establish a predictive relationship between silicate melt structure and transport properties.
• To overcome limitations of experimental methods for determining viscosity and diffusivities.
• To enable quantitative estimation of transport coefficients using readily available structural data.

Main Methods:

• Molecular-dynamics simulations were employed to model silicate melts.
• Analysis focused on the relationship between diffusivities and excess entropy.
• Excess entropy was approximated using radial distribution functions and static structure factor data.

Main Results:

• A strong correlation was identified between melt diffusivities and excess entropy across various compositions, temperatures, and pressures.
• Approximations for excess entropy were successfully derived from radial distribution functions.
• A structure-thermodynamics-dynamics relationship was established for silicate melts.

Conclusions:

• Transport properties of silicate melts can be quantitatively estimated using experimental static structure factor data.
• This approach provides a powerful alternative to difficult experimental measurements.
• The findings advance the understanding of melt behavior under high-pressure, high-temperature conditions.