Scanning tunneling microscopy observations of homoepitaxial growth on vicinal Si(001) and of coarsening of Si islands are used to develop a model of growth based on a configuration‐dependent activation energy to hopping. In the model four contributions to this energy barrier are proposed: the activation energy to surface diffusionEs, the dimer formation energyEdand two directional interaction energies between neighboring atoms not forming a dimer,E∥andE⊥. Monte Carlo simulations are employed to compare experimental results with the results of the tested model and to deduce the atomic interaction energies:Es=(1.15±0.1) eV,Ed=(0.45±0.10) eV,E∥=(0.20+0.2−0.14) eV,E⊥=(0.10+0.1−0.07) eV. Preliminary results of simulations, including anisotropic diffusion, are presented.