Dear Mohammad,

This is not so simple. Every unit cell you describe with FLEUR is periodically repeated. This implies that a finite overall charge of a unit cell translates into an infinite charge for the whole crystal and thus the Coulomb energy diverges. But you can employ certain tricks to perform such calculation nevertheless. These are, however, not accessible via our input and thus you have to modify the code itself. Gustav will get in contact with you to explain to you what options there actually are.