  We present a new scheme to extract numerically ``optimal'' interatomic
potentials from large amounts of data produced by first-principles
calculations. The method is based on fitting the potential to ab initio atomic
forces of many atomic configurations, including surfaces, clusters, liquids and
crystals at finite temperature. The extensive data set overcomes the
difficulties encountered by traditional fitting approaches when using rich and
complex analytic forms, allowing to construct potentials with a degree of
accuracy comparable to that obtained by ab initio methods. A glue potential for
aluminum obtained with this method is presented and discussed.
