Dissolution anisotropy of pyroxenes: a surrogate model for steady-state enstatite dissolution resulting from stochastic simulations of the hydrolysis process
Publisher DOI
Abstract
Over recent decades, the field of mineral dissolution kinetics has undergone a spectacular evolution, with an increasingly detailed description of the atomic-scale mechanisms of fluid–solid interactions. The development of probabilistic dissolution models has played a prominent role in this evolution, as they allow for bridging the outputs of ab initio calculations to macroscopic observables such as dissolution rates and nanoscale surface features. It is however admitted that these models cannot be easily adapted to simulate natural systems at large space and time scales due to the restricted dimensions and durations that can be simulated numerically. In the present study, we demonstrate that the steady-state outputs of the face-specific stochastic treatment of enstatite dissolution, which was experimentally validated in a previous paper, can be boiled down to a single analytical expression under the following form: rbulk(hkl) = kPMg–O–MgαPMg–O–SiβPSi–O–Siγ, where rbulk(hkl) is the steady-state dissolution rate of a defect-free (hkl) face [Å/iteration], PM–O–M′ stands for the bond-breaking probability of the M–O–M′ bond, and k, α, β, and γ are fitting parameters adjusted following the outputs of the stochastic simulations. When dislocations outcrop at the surface of a given (hkl) face of enstatite, the relation then becomes r(hkl) = rbulk(hkl) + rdislocation(hkl)(PMg–O–Mg, PMg–O–Si, PSi–O–Si), where rdislocation(hkl) stands for the contribution of the dislocations to the overall dissolution rate. The derivation of simple analytical expressions to get steady-state rate data that are similar to those obtained using stochastic dissolution models, may contribute to efficiently parametrizing the bond-breaking probability of various atoms for pyroxene solid solutions, and raises the question of the extension of such surrogate expressions to other silicate structures. Finally, the development of surrogate models such as those reported here represents one of the possible strategies for upscaling dissolution processes from the atomic scale to the micrometer scale.
Date Issued
2020-05-21
Publication Type
Article
Language(s)
en
Author(s)
Daval, Damien | |
Ackerer, Philippe |
Additional Credits
Journal
The Journal of Physical Chemistry C
Publisher
American Chemical Society
ISSN
1932-7447
1932-7455
Access(Rights)
restricted