MOLECULAR DYNAMICS SIMULATION OF LAYERED DOUBLE HYDROXIDES

摘要

The interlayer structure and the dynamics of Cl~- ions and H_2O molecules in the interlayer space of two typical LDH phases were investigated by molecular dynamics computer simulations. The simulations of hydrocalumite, [Ca_2Al(OH)_6]Cl·2H_2O, reveal significant dynamic disorder in the orientation of interlayer water molecules. The hydration energy of hydrotalcite, [Mg_2Al(OH)_6]Cl·nH_2O, is found to have a minimum at approximately n = 2, good agreement with experiment. The calculated diffusion coefficient of Cl~- as an outer-sphere surface complex is almost three times that of inner-sphere Cl~-, but is still about an order of magnitude less than that of Cl~- in bulk solution. The simulations demonstrate the unique capabilities of combined NMR and MD studies to understand the structure and dynamics of surface and interlayer species in mineral/water systems.