Diffusion mechanisms of dimers adsorbed on periodic substrates

We have utilized static minimum-potential-energy calculations to determine microscopic diffusion mechanisms of the simplest molecular adsorbate, namely a dimer, on a periodic substrate. We consider a rigid homonuclear dimer physically adsorbed on a SC(100) crystal surface by means of a Lennard-Jones potential. We show that, by varying the dimer length relative to the lattice constant, a wide range of rich and varied diffusion behavior can be achieved. The model has experimental analogs and implications, which will be discussed.