[Wien] a question regarding space group and primitive cell

[Stefaan Cottenier]

>                                We have done a calculation for a material
> having space group *Pnma.* The material has *4 in equivalent* atoms and
> total *20 atoms/unit cell*. Now if we use all the 20 atomic coordinates
> of previous calculation and make *all of them inequivalent by changing
> the space group to Primitive* then whether the calculation will give the
> same results as earlier calculation??.....I am asking this question
> because the structure (in Xcrysden) seems to be different.........

A static calculation (one scf-cycle) must give you the same result, yes. 
It will only take more time, because one can profit less from symmetry.

If you allow geometry optimization, the final geometry might be 
different, however: perhaps an atom that is not longer constrained by 
symmetry might want to move to a different place.

In order to convince yourself whether or not both structures are 
identical, it is much cheaper to inspect the neighbours rather than 
performing an scf cycle. Do 'x nn' for both structures, and compare the 
distances in case.outputnn.

Stefaan