I am looking into double perovskite materials. One of the possible materials is $\ce{Cs4CuSb2Cl12}$. Now, although there are a few papers which have done ab intio calculations but none of the common open databases have a CIF for this structure(COD and materials project). The paper which I am currently looking into has submitted their data to ICSD, but I do not have access.
Due to which I have decided to start working on my own cif file. An older answer gave a brief description on how to do this using VESTA (and I am also comfortable with the software), but I still have some doubts. Mainly how does one calculate the spatial coordinates of each atoms and how do we add the term U (which I suppose is the energy of some sort)?
If anyone has any idea how I can obtain a CIF or how to go about finding the coordinates and finally making a CIF (please also mention what other information is needed apart from the space group and lattice parameters)