Previous calculations of the structures of isomers of phosphorus clusters up to P11 (density functional calculations with simulated annealing, local spin density approximation to the exchange-correlation energy) have been extended to arsenic clusters. The structures of As(n) clusters are characterized by an almost uniform expansion (approximately 9%) of the corresponding P(n) isomers. All cluster isomers have also been studied using a nonlocal, gradient corrected (Becke-Perdew) energy functional. While the structures are almost unchanged, there are significant improvements in the cohesive energies of all clusters. We present a simple picture to show that the improvements arise from contributions both in the atoms and near the "surface" of the clusters.