Mineral dissolution is a fundamental process in geochemistry and materials science. It is controlled by the complex interplay of atomic level mechanisms like adatoms and terraces removal, pit opening, and spontaneous vacancy creation that can be gradually activated at different energies. Though the development of a comprehensive atomistic model is key to go deeper into the understanding of this phenomenon, existing models have failed to reproduce the abrupt dependence of the dissolution rate with the Gibbs free energy ( G). Herein, a new atomistic kinetic Monte Carlo (KMC) model is presented, which, invoking the microscopic reversibility of chemical reactions, captures the experimentally observed sigmoid dependence of the dissolution rate and provides new insights on the concomitant dissolution mechanisms. As a salient result, the model predicts the possible existence of unreported close-to-equilibrium dissolution modes where spontaneous vacancies creation and pit opening can occur before adatom and terrace removal.

Quartz dissolution is a frequent process in geochemistry and materials science. It is controlled at the atomic scale by the sequential hydrolysis reactions and breakage of siloxane bonds, the surface topography, and the Gibbs free energy difference ΔG between the solid and the solution. Atomistic simulations have provided valuable topographic information about quartz dissolution and reaction energy barriers. However, with the current interpretation of the data, serious discrepancies persist between the predicted dissolution rates R dis and the macroscopic dissolution activation energy E a compared to their experimental counterparts. In this work we show that both quantities can be reconciled using a kinetic Monte Carlo (KMC) atomistic model based on bond-by-bond reactions and R dis and E a can be jointly reproduced. In addition, the obtained etch pit shapes for different quartz planes are in agreement with the experimentally reported ones: V-shape striations in {001}, rectangular pyramidal pits in {100}, and trapezoidal semipyramidal pits in {101}. We also study the dissolution rate dependence with ΔG by introducing chemical reversibility in the KMC model, obtaining again results in good agreement with experiments. This work highlights the importance of understanding the mechanisms taking place at the nanoscale to describe macroscopic properties and provides the basic ingredients to extend this study to other minerals and/or dissolution conditions.

KIMERA is a scientific tool for the study of mineral dissolution. It implements a reversible Kinetic Monte Carlo (KMC) method to study the time evolution of a dissolving system, obtaining the dissolution rate and information about the atomic scale dissolution mechanisms. KIMERA allows to define the dissolution process in multiple ways, using a wide diversity of event types to mimic the dissolution reactions, and define the mineral structure in great detail, including topographic defects, dislocations, and point defects. Therefore, KIMERA ensures to perform numerous studies with great versatility. In addition, it offers a good performance thanks to its parallelization and efficient algorithms within the KMC method. In this manuscript, we present the code features and show some examples of its capabilities. KIMERA is controllable via user commands, it is written in object-oriented C++, and it is distributed as open-source software.

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