Comment on "Mineral-water reactions in Earth's mantle: Predictions from Born theory and ab initio molecular dynamics" by Fowler et al. 2024 (Geochim. Cosmochim. Acta 372, 111-123)

TL;DR

This comment clarifies discrepancies in dielectric constant calculations of water under extreme conditions, emphasizing the importance of methodological accuracy in dipole moment calculations for Earth's mantle modeling.

Contribution

It identifies and explains the methodological differences affecting dielectric constant results in high-pressure water simulations.

Findings

Pan et al.'s results are well-converged and reliable.

Discrepancies stem from dipole moment calculation methods.

Methodological issues impact modeling of mineral-water interactions.

Abstract

This comment addresses discrepancies in dielectric constant calculations of water under extreme conditions (~10 GPa and 1000 K) between Fowler et al.'s recent study [Geochim. Cosmochim. Acta 372, 111-123 (2024)] and the earlier work by Pan et al. [Proc. Natl. Acad. Sci. 110, 6646-6650 (2013)]. Through reproduced ab initio molecular dynamics (AIMD) simulations using the CP2K code with extended duration and identical system size, we rigorously validate that Pan et al.'s original results (39.4) are well-converged, contrasting with Fowler et al.'s reported value of 51. The observed discrepancy cannot be attributed to simulation duration limitations, but rather to methodological differences in dipole moment calculation. Our analysis highlights critical issues in the treatment of dipole moment fluctuations in periodic systems within the framework of modern theory of polarization. This clarification has significant implications for modeling mineral-water interactions in Earth's mantle using Born theory.