Dissolution and growth of (1014) calcite in flowing water: estimation of back reaction rates via kinetic Monte Carlo simulations

摘要

Although calcite is an important mineral for many processes, there have been relatively few simulations of its growth and dissolution behavior. Such simulations are complicated by the multitude of defect types and by the asymmetry of the crystal. The present work combined a kinetic Monte Carlo technique with the Kossel crystal (100) simple cubic concept and the Blasius boundary layer model to simulate the simultaneous growth and dissolution of the (1014) calcite cleavage surface in flowing water. The activation energies of the back reaction (growth) were determined from those of the forward reaction (dissolution) by obtaining agreement with cleavage-step morphologies and step dissolution velocities over a range of flow rates previously measured using an atomic force microscope. The kinetics were dominated by diffusion events on the solid/fluid interface and in the fluid, as expected. The relative magnitudes of the desorption and adsorption activation energies were consistent with experimental data, entropic arguments, and crystal roughening theories. Quantitative agreement with measured step velocities was best when the boundary layer parameters were given physically reasonable values, indicating that the model is self-consistent.