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Recent experiments suggest that InAs quantum dots grown on GaAs(001) undergo a shape transition during growth from ’hut’ to ’dome’-like shapes, similar to Ge quantum dots on Si. From a thermodynamic point of view, quantum dot formation is governed by the energetic balance between the energy gain due to strain relief and the energy cost due to formation of quantum dot side facets and edges. In order to account for both contributions, we have developed a carefully parametrized bond-order potential. Its analytical form follows the previous suggestions by Abell and Tersoff, but the newly determined parameters have been fitted to reproduce the elastic constants as well as properties of both GaAs and InAs low-index surface reconstructions obtained from density-functional theory calculations. The potential describes the elastic constants with less than 10% deviation and the considered surface energies within 10 meV/Å^2. The results of our calculations are helpful in analysing the energetics of different experimentally observed shapes, and of incomplete layer growth on the facets.