VASP Forum

Dear All,
I was trying to check all the electron and VASP results for the HOMO energy of the Ar atom. But found discrepancies in results

For all electron code (Q-Chem) with cc-pvdz basis set HOMO=-14.98340436 eV
whereas from VASP I am getting HOMO=-13.9169 eV

Omega= 0.40 bohr^-1

I am using the following INCAR with Ar_GW pseudopotential and a 15 A cubic box

System Bulk
NELM =100
ISMEAR = 0
SIGMA = 0.001
EDIFF = 1E-5
KPAR=4
LHFCALC = .TRUE.
LMODELHF = .TRUE.
HFSCREEN = .75589199999987626047 # 0.40 bohr^-1
AEXX=1.0
BEXX=0.00
ALGO = A
LORBIT=11
LASPH = .TRUE.
ADDGRID = .TRUE.
ISPIN=2
ENCUT=500
LVTOT=.TRUE.

Note that the PBE results match. I request urgent help.

Thanks
Subrata Jana

It will work if I put AEXX=0.9999 instead of 1.0
This is very strange.

Hi,

In the code (fock.F) the LDA/GGA/MGGA correlation energy is set to zero if AEXX=1.0:

         ! for HF type calculations and full exchange, no correlation is usually included
         IF (AEXX==1.0) THEN
            XC%ALDAC=0.0_q
            XC%AGGAC=0.0_q
            XC%AMGGAC=0.0_q
         ENDIF

In this case, to include the correlation energy it is necessary to set these variables to 1.0 in INCAR:

ALDAC=1.0
AGGAC=1.0
AMGGAC=1.0