# Atomistic simulations of molten carbonates: thermodynamic and transport properties of the Li2CO3-Na2CO3-K2CO3 system

## TL;DR

This study develops a comprehensive atomistic simulation model for molten alkali carbonates, accurately predicting their thermodynamic and transport properties across conditions relevant to Earth's mantle and technological applications.

## Contribution

It introduces a novel, validated classical force field for molten alkali carbonates applicable over wide temperature, pressure, and compositional ranges.

## Key findings

- Good agreement with experimental data on thermodynamics and transport properties.
- First reliable molecular model covering extensive conditions for molten alkali carbonates.
- Provides insights into geochemical processes and potential technological uses.

## Abstract

Although molten carbonates only represent, at most, a very minor phase in the Earth's mantle, they are thought to be implied in anomalous high-conductivity zones in its upper part (70-350 km). Besides the high electrical conductivity of these molten salts is also exploitable in fuel cells. Here we report quantitative calculations of their properties, over a large range of thermodynamic conditions and chemical compositions, that are a requisite to develop technological devices and to provide a better understanding of a number of geochemical processes. To model molten carbonates by atomistic simulations, we have developed an optimized classical force field based on experimental data of the literature and on the liquid structure issued from ab initio molecular dynamics simulations performed by ourselves. In implementing this force field into a molecular dynamics simulation code, we have evaluated the thermodynamics (equation of state and surface tension), the microscopic liquid structure and the transport properties (diffusion coefficients, electrical conductivity and viscosity) of molten alkali carbonates (Li2CO3, Na2CO3, K2CO3 and some of their binary and ternary mixtures) from the melting point up to the thermodynamic conditions prevailing in the Earth's upper mantle (~ 1100-2100 K, 0-15 GPa). Our results are in very good agreement with the data available in the literature. To our knowledge a reliable molecular model for molten alkali carbonates covering such a large domain of thermodynamic conditions, chemical compositions and physicochemical properties has never been published yet.