# Meaning of total ground state energy in periodic DFT calculations

1. Jan 16, 2015

### Derivator

Dear all,

periodic DFT codes (e.g. VASP) effectively simulate an infinite crystal due to the periodic boundary conditions. However, the energy value that one obtaines at the end of a simulation if finite. Frankly, I'm quite confused right now.

Is the energy to be understood 'per unit cell'? Why is the energy value not infinite?

Cheers,
derivator

2. Jan 16, 2015

### DrDu

Yes, it is per unit cell.