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We have used a combined tight-binding/density functional theory approach to search for the optimal structures of small and intermediate-sized Ge n clusters, with n<= 30. The approach uses a computationally fast tight-binding method to survey the cluster energy surface for candidate structures. The search employs a novel single-parent genetic algorithm (SPGA) that successfully located the global minima for Si clusters in the same size range (Rata et al., Phys. Rev. Lett. 85, 546 (2000)). Gradient-corrected density functional theory (DFT) calculations are then performed to study the candidate structures in more detail. We show that our tight-binding model and the DFT yield consistent global minima for clusters up to n= 10. The initial results of the SPGA searches for larger clusters show that prolate Ge n clusters remain more stable than compact structures beyond n= 26, the size at which Si clusters are known to …