Hi Tim, you don't necessarily want to find the global minimum (...)
this contradicts the definition of crystallographic structure refinement. If finding the global minimum is not what you ultimately want then either the refinement target or model parameterization are poor. Clearly, given complexity of refinement target function profile (in case of macromolecules) we unlikely to reach the global minimum; however, reaching it is what we aim for (by definition and construction of refinement program) . Pavel
