Hi, from the FFT documentation: AXIS <fast> <medium> <slow> <https://www.ccp4.ac.uk/html/fft.html#axis-fast-medium-slow>
*In general DO NOT change the axis order unless you are in P1 or are very sure you know what you are doing! This is permitted if your map is being calculated using the routines for P1 or P222, but not otherwise.* <fast> <medium> <slow> are the letters X, Y and Z in the appropriate order. Note that many of the FFT space-group specific routines have FIXED axis orders. In general these are Y,X,Z for those which have rotation axes along c, and are best output with z-sections (all space-groups with space-group number greater than 18 (P21212)). For P1, the monoclinic space-groups, and space-groups 16 (P 2 2 2), 17 (P 2 2 21) and 18 (P 21 21 2), the required axis order is Z,X,Y, which gives y-sections. If this keyword is left out (the recommended procedure), and the map is calculated in FFT space-group P1 (the FFTBIG default) then the standard order for TRUE space-group is used, *i.e.* Z,X,Y for P1, the monoclinic space-groups, and space-groups 16, 17 and 18; for all higher symmetry space-groups the standard axis ordering will be Y,X,Z. Otherwise, note that any axis permutation must make sense in the space-group used for the FFT, *e.g.* the P21 FFT (sg4) always generates a 21 axis along the section axis, through the origin. Axis permutation is only permitted in a few space-groups and should probably by cyclic: 1, 2, 19, 21, 23, 47. In space-group 19, only cyclic permutations are valid, *i.e.* Y,X,Z (default); Z,Y,X; or X,Z,Y; others will give WRONG ANSWERS. Cheers -- Ian On Tue, 21 Jun 2022, 14:12 fuxingke, <fuxingke0...@163.com> wrote: > In ccp4, I can use "Generate Patterson Map" to generate Patterson map > in "Map & Mask Utilities". But, I found a serious problem. When I use a set > of data with spacegroup P21 and the position of atom is kown, the length > of w-axis in the Patterson map is not equal to cell parameters c. What's > more, the position of Patterson peaks are also different from the > interatomic vectors. The parameter is as below. > Why the Patterson map is different? How can I avoid this problem？Is > there any other better method to calculate the Patterson map? > [image: 0] > > I'm looking forward to your reply. > > Regards > > > > Best wishes, > > Fu Xingke > Institute of Physics CAS > > > ------------------------------ > > To unsubscribe from the CCP4BB list, click the following link: > https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1 > ######################################################################## To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1 This message was issued to members of www.jiscmail.ac.uk/CCP4BB, a mailing list hosted by www.jiscmail.ac.uk, terms & conditions are available at https://www.jiscmail.ac.uk/policyandsecurity/
