lavn2
Hi, I have downloaded a CIF for Mn3O4 which is in the second origin for space group I41/amd. In Topas, the atomic sites look like this:
space_group "I 4 1 / a m d"
site Mn1 x 0 y 0.25 z 0.875 occ Mn+2 1. beq Mn_beq_Mn3O4 0.5
site Mn2 x 0 y 0.5 z 0.5 occ Mn+3 1. beq =Mn_beq_Mn3O4;
site O1 x 0 y 0.4722 z 0.2589 occ O-2 1. beq @ 0.5
However, when I use view_structure it looks all wrong, with the atoms not in the right places. I realise this is because Topas is expecting the first origin for the space group. To resolve this I tried adding this line:
site origin num_posns 0 x 0. y 0.5 z 0.5 occ D 0
while varying the x,y,z parameters to see if this led to changes in the origin. However, this hasn't actually made any difference when outputting a CIF file and viewing it, or when using view_structure, which makes me think I must be doing something wrong. Can anyone explain what is the right way to account for different origins in CIFs, in a Topas structural phase?