Quantitative prediction of kink site formation rate on calcite and barite using metadynamics.
EMSL Project ID
28091
Abstract
Quantitative kinetic models in geochemistry are often hindered by a lack of knowledge of likely reaction pathways. Furthermore, experimental data of mineral surface reactions is often ambiguous, where the observed rate is a function of the individual rates of several different species. Computational methods are now sufficiently advanced to potentially quantitatively estimate the rates of important geochemical reactions. One recent method of substantial interest is metadynamics in which the potential energy of the system is explored through the periodic addition of Gaussian-shaped repulsive energy wells. This forces the reaction away from stable or metastable states and increases the sampling of high energy transition states. In this User Proposal, we are asking for 150,000 processor-hours on mpp2 to work with two EMSL scientists, Drs. Gregory Schenter and Sebastien Kerisit. The goal is to first formalize the connection between metadynamics and the potential of mean force, a commonly used way to estimate a rate constant for a reaction. Once created, we will apply this method to an important reaction for crystal growth and dissolution: the kink site formation reaction. That is, at saturations close to equilibrium, the rate that a given crystal dissolves or grows is dominated by the movement of monomolecular steps on the surface of the mineral. The velocity of these steps is thought to be limited by two reactions, double kink site formation and single kink site propagation. We intend to simulate the former reaction on two different minerals, calcite and barite, because they are environmentally and industrially important and high quality experimental estimates of the kink site formation rate exist to which the computational estimates can be compared. Additionally, the PI and co-PIs have had experience simulating reactions on both of these minerals and have molecular dynamics force fields ready that have been extensively tested and readily applied to the metadynamics method.
Project Details
Project type
Exploratory Research
Start Date
2007-12-01
End Date
2008-12-07
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members