[Wien] structure relaxation requirement for input atom positions

[qiang]

Dear all:

As we know that given a starting structure model, molecular Dynamics can be
used to refine atom to their energy (force) equilibrium position. 
Obviously, if the starting structure model is too far away from the correct
one, 
the refinement may crash or may not lead to the right positions.
For a successful structure relaxation, does anyone know the general
requirement for a starting structure model?  How close to the correct should
a starting structure model be? (e.g. the starting atom positions should be
within 0.5 A away from the correct positions.)  Is there any ref. about this
problem?

Best regards

Qiang