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Which programs require that the data be the 'standard' a.u.? None of mine require this. George On 05/29/2012 03:44 PM, Ian Tickle wrote: > Mark, thanks for pointing that out, I see it now: > > In P321 the only possible alternate indexing is (-h, -k, l): this is a > 2-fold || c which is an operator of the hexagonal lattice but is not > an equivalent reflection. > > The standard CCP4 a.u. is h = k, l>= 0 or h> k, k>= 0, so for > example (3,2,1) would be in the standard a.u. (3> 2 and 2>= 0). In > the alternate indexing this would be (-3, -2, 1); however it's > impossible to transform this to the a.u. with any non-inverting > equivalent. The only possibility is to invert the hand, i.e. to (3, > 2, -1) which is again in the a.u.. > > So the required re-indexing operator to match (3, 2, -1) with (3, 2, > 1) is (h, k, -l) which reindex won't allow without the LEFT keyword > (and you would be well-advised to avoid doing it with phase columns!). > > Cheers > > -- Ian -- Prof. George M. Sheldrick FRS Dept. Structural Chemistry, University of Goettingen, Tammannstr. 4, D37077 Goettingen, Germany Tel. +49-551-39-3021 or -3068 Fax. +49-551-39-22582