http://www.cryst.ehu.es/cgi-bin/cryst/programs/nph-wp-list

Hope, it will solve the problem

Dear Ameer, if you know space group and lattice parameters introduce any reference frame on any definite atom. So we get coordinates for any rhe other atom. It is simple formal operation.

http://www.cryst.ehu.es/cgi-bin/cryst/programs/nph-wp-list

Hope, it will solve the problem

Dear Ammer,

it really depends on the crystal system and the compound. For example, the ideal perovskite structure (ABO3) is described completely by the space group Pm-3m and the cubic lattice parameter. This fixes all atoms. In less symmetric space groups (i.e. P4mm) the atoms will get freedom on their positions.

Hope this is an approach to Your question.

Best regards,

Wolfgang

Dear Dr Ammer

The attached picture is the example on how to put atom in cubic ABO3 (Pm-3m) from International Table for Crystallography A page 673.

Example if u put atom at 0,1/3,1/4 (0, y, z ), by the symmetry operation you'll get 48 atoms at all faces = 1/2 x 48 = 24 atoms /cell,  wyckoff letter is 24k.

In contrast if u put at 0,0,0 than you'll get 8 atoms all corners = 1/8 x 8 = 1 atoms /cell , wyckoff letter is 1a, (let this to be A)

• 1/2,1/2,1/2 give u 1 atom at the center, wyckoff letter is 1b, (than this is B)
• 0,1/2,1/2 give u 6 atom at all the faces = 1/2 x 6 = 3 atoms /cell, wyckoff letter is 6f, give u the 3 Oxygen atoms (this O3).

Or if u wanna start from the structure (known space group), you should know how many of the particular atom inside the unit cell and their equivalent position, than u can get its coordinat.

Following the answer of W. Milius, I confirm that for sinple and high-symmetry structures the positions of the atomns are fixed by symmetry and the determination of the structure is straighforward. However, frankly speaking, resarchears using crystallography should know at least the basis of this science: structure determination is a complex problem and cannot be faced without a specific preparation.

The traditional way to solve a crystal structure is by Xray diffraction. Electron or neutron diffraction are also possible. The lattice constants can be determined from the diffracted intensities and the space group can be determined by observing their systematic absences. The determination of the space group is often reduced to a few possible cases and sometimes it is unique. Nowadays, the solution of the structure based on the measured intensities is straightforward since the discovery of dual phase retrieval algorithms (charge flipping or else). If the space group is uniquely defined by the systematic absences and if all atoms occupy variable free special Wyckoff positions, then a solution can be found by analysing the Wyckoff positions only. Such cases occurs seldomly. Diamond is such an example, ABO3 is another example.