Geometry optimization: dependence on initial geometry One would think that initial configuration should not significantly impact the final optimized geometry. Starting with two moieties, the final "optimized" geometry is not unique and depends highly on how they are placed initially. Is there a way to avoid this? Otherwise one could never be sure that they have ended up with the global minimum.
Starting with two moieties, the final "optimized" geometry is not
  unique and depends highly on how they are placed initially. Is there a
  way to avoid this?


Yes and no. No, because, as OP anticipated, starting from an input geometry the optimisation algorithm will indeed find the closest (from the algorihtm point of view) local minimum and not necessarily the global one. And yes, because by performing an extensive conformational analysis, one in principle can find structures that correspond to all possible local minima and then identify the global one.