Re: [ccp4bb]: xyzlimit

[Clemens Vonrhein <vonrhein@GlobalPhasing.com>]

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> > There are consistent inconsistencies with real space asymmetric units
> > between the various programs :-(
> >
> 
> Ah, yes, this is an ellegant description of the situation.
> I actually think that only ARP is 'inconsistent', but its very
> polite on telling you what it really needs as AU limits.

ARP is not alone: I can think of other 'inconsistencies' too. Compare
the asymmetric units FFT is using with the ones SFALL requires:

  Spacegroup      FFT                           SFALL
               X      Y       Z           X      Y       Z
    P21212   0. 1.  0. 0.25 0. 1.       0. 1.   0. 1.   0. 1.
    C2221    0. 0.5 0. 0.25 0. 1.       0. 1.   0. 1.   0. 1.
    C222     0. 0.5 0. 0.25 0. 1.       0. 1.   0. 1.   0. 1.
    F222     0. 0.5 0. 0.25 0. 1.       0. 1.   0. 1.   0. 0.25
    I222     0. 0.5 0. 0.25 0. 1.       0. 1.   0. 1.   0. 1.
    P4212    0. 1.  0. 0.25 0. 1.       0. 1.   0. 1.   0. 1.
    P4122    0. 1.  0. 1.   0. 1.       0. 1.   0. 1.   0. 0.125
    P4322    0. 1.  0. 1.   0. 1.       0. 1.   0. 1.   0. 0.125
    I422     0. 0.5 0. 0.25 0. 1.       0. 1.   0. 1.   0. 1.
    P3       0. 1.  0. 1.   0. 1.       0. 0.67 0. 0.67 0. 1.
    P622     0. 1.  0. 1.   0. 1.       0. 0.67 0. 0.67 0. 1.
    P6322    0. 1.  0. 1.   0. 1.       0. 0.67 0. 0.67 0. 1.
    F23      0. 0.5 0. 0.25 0. 1.       0. 1.   0. 1.   0. 0.25
    I23      0. 0.5 0. 0.25 0. 1.       0. 1.   0. 1.   0. 1.
    F432     0. 0.5 0. 0.25 0. 1.       0. 1.   0. 1.   0. 0.25
    F4132    0. 0.5 0. 0.25 0. 1.       0. 1.   0. 1.   0. 0.25
    I432     0. 0.5 0. 0.25 0. 1.       0. 1.   0. 1.   0. 1.

(I'm not totally sure about these different requirements: some of them
are probably due to the differences in spacegroup-specific routines
FFT and SFALL use. But it gives you an idea.)

So sometimes you need to put a MAPMASK/EXTEND step between. Anyway,
once you know the various asymmetric unit definitions you can easily
extend your maps.

Cheers

Clemens


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