Wrong total energies for charged systems

[jmoussa]

I've been trying to use the delta-SCF approach to calculating positions of impurity levels and have found a problem with VASP total energies.

The simplest example that demonstrates this problem is the primitive unit cell of diamond. I converge the ground state geometry and total energy and then freeze the geometry and calculate the total energy of diamond with one hole per unit cell (admittedly not a physically relevant calculation) and take the total energy difference, E(N) - E(N-1). PWSCF and fhi-AIMS both give similar results for this, 10.5 eV and 10.6 eV, but VASP gives different results, which are strongly pseudopotential dependent: 8.6 eV for the soft and hard PAWs, 7.2 eV for the standard carbon PAW. This error is purely coming from the E(N-1) term. The KS spectra all agree and based on the decomposition of total energy give in VASP, this looks like a problem in the V(G=0) potential energy term.

Using deltaSCF on molecules in large supercells doesn't seem to have this problem in VASP, which makes it all the more strange.

[support_vasp]

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