Those pictures are nicely done. You have more patience with Paint than I do!
Your last diagram is nearly perfect, with only one problematic detail.
First, what is right in the picture:
- All the symmetry elements are there with the 21
screw axis parallel to the a-axis. The mirror perpendicular to the b-axis. The a-glide plane perpendicular to the c-axis. No problem, you have the space group P21ma.
- All the symmetry-generated positions are correct. For example if you start from the position x,y,z and apply the mirror perpendicular to b-axis, you end up at the position x,-y,z. No problem.
- The stereographic projection is correct.
- The numbers on the right showing (general positions, symmetry operations and reflection conditions) look great but, and here is the problem, they correspond to the space group Pmc21.
For example, if you look at the mirror in the symmetry operations list, you see: m[0,y,z]. The mirror is perpendicular to the a-axis.
If you look at the screw axis, you can read: 21
(0,0,z)[0,0,1/2]. (0,0,z) means that 21
is parallel to the c-axis.
What you have here corresponds to Pmc21
, not to P21
To summarise, the picture corresponds to P21ma but the table corresponds to Pmc21. I guess you copied the picture from the international tables and added the right axis permutation, but you forgot to permute the coordinates as well.
This is easily corrected by a cyclic permutation:
in Pmc21 becomes in P21ma
1. x,y,z 1. x,y,z
2. -x,y,z 2. x,-y,z
3. x,-y,1/2+z 3. 1/2+x,y,-z
4. -x,-y,1/2+z 4. 1/2+x,-y,-z
Are you OK with it? If yes, permuting the rest of the Pmc21 table in a way that it belongs to P21ma should be easy game. It works exactly the same as above. After that, it's all done.