Hello @ Abdelhamid Ait m’hid,

You can look up the structure of copper in any physics textbook (e.g. Introduction to Solid State Physics by Kittel). Copper crystalizes in the face-centered cubic lattice structure. Also, you may search different publications to see if someone had carried out DFT calculations for copper and try to see if your results are similar to what they obtained.

I hope this helps.