UnitCell does not require initial estimates for cell contants. Fine.
But you need to give it reflection positions and hkl Miller indices.
Right ? So that if you have Miller indices, you have somewhere initial
estimates for cell constants ! Probably from a previous indexing...
I have not found a situation where you could know the Miller
indices and not an initial estimate for the cell constant (except the case
you have lost your data :-). Could you give more details ?
Just work more on your program. When you will be able to say
that UnitCell does not require estimates for cell constants nor
knowledge of the Miller indices, you will have obtained an
automatic cell indexation program ;-).
Armel
Out of lethargy - and not seing Rietveld-football relation, apart C60