Nucleation and growth of Pd on cleaved MgO(001) surfaces were studied by va
riable-temperature atomic force microscopy in the temperature range 200-800
K. Constant island densities (similar to 3x10(12)cm(-2)) were observed ove
r a wide temperature range, indicating nucleation kinetics governed by poin
t defects with a high trapping energy. These results are compared to a rate
equation model that describes the principal atomistic nucleation and growt
h processes, including nucleation at attractive point defects. Energies for
defect trapping, adsorption, surface diffusion, and pair binding are deduc
ed, and compared with recent nb initio calculations.