Widespread interest in the field of epitaxy has stimulated us to perform a first principles atomistic calculations dealing with the energetics of bicrystals. Using a self‐consistent pseudopotential approach we have calculated total energy as a function of growth sequence of a metal on a semiconductor surface. The prototype system we study is the pseudomorphic growth of aluminum on an unreconstructed Ge(001). For Al(001)–Ge(001) in the epitaxial relationship (001) [100]Al∥(001) [110]Ge where the [100]Al axis has been rotated 45° with respect to the Ge[100]a small lattice mismatch might allow coherency. We present the results of total energy calculations starting from submonolayer coverages of Al to multilayer deposition of metal. Of the two possible symmetric sites (bridge and on top) where the overlayer can begin to grow, our calculation favors the bridge site. Upon increasing the overlayer thickness we found a striking change (∼35% increase) in the interplanar distance between the substrate and the overlayer. The absolute value of the interplanar distance increased from about 1.2 to about 1.7–1.8 Å. An important observation we wish to make is that the interplanar distance between two expitaxially grown systems rapidly tends to stabilize at the average interplanar separation of the constituents. Even though our calculations are for a specific system, we suggest that this might be more generally applicable. An experimental corroboration of this fact should be very valuable. We also present results for the unsupported aluminum film and show that its lattice constant is contracted by about 10% as compared to the bulk value. From this we are able to calculate a realistic value for the elastic energy contribution to the total energy. Some important implications of the thin film effect for the structural properties of the overgrowth are briefly discussed.