CdTe surfaces: Characterizing dynamical processes with first-principles metadynamics

We study dynamical processes at CdTe surfaces using ab initio metadynamics simulations. The c(2X2) to (2X1) transition of the Te-terminated (001) surface is found to involve a "c(2X2) + (2X1)" intermediate, consistent with experiment, and crossing of similar to 0.5 eV free-energy barriers at 400 K. Higher free-energy barriers (1.6-2.5 eV) are estimated for desorption of a Cd ion from Cd-terminated (001) and a CdTe unit from either Te-terminated (001) or (110) surfaces. Cd and Te exhibit a very different behavior. Concomitant to desorption, Te surface diffusion is observed as well as Te dimerization and bulk-surface Cd exchange events. (C) 2010 American Institute of Physics. [doi:10.1063/1.3499430]