Issue with Ti_sv PPS and RPBE functional

[iciquser]

Greetings,

I'm having a strange problem when computing the adsorption energy for titanium oxide.

I'm using the Ti_sv PPS with the RPBE functional, VASP version 5.3.3 (but I've also tested the thing on a 5.2.12)

The simulations of the system (Ionic Optimization) with the adsorbed molecule and the clean surface terminate without problems.
However, when I compute the adsorption energy (E_sys - E_surface -E_mol) I obtain an endothermic value of 0.57.

Please notice that I've ran the same calculations with (PBE + Ti_sv) and (RPBE + Ti_pv) and in both cases the adsorption energy is exothermic of around (1.4-1.9 eV), as it should be.
When I've used the same PPS (Ti_pv or Ti_sv) the final structures (both of the adsorbed and the clean surface) are pratically the same (coordinate difference < 0.0035).
I remember I had some other issues with RPBE functionals as it seems the case, did anyone had problems with that?

Other notes:
I have a vacancy in the surface and two delocalized electrons, I have used the LDA+U and magnetic moment plus spin polarized calculations. However the final magnetization is the same for the systems and I have used the same INCAR for every calculation. I've applied grimme vdW-D2 for the dispersions.

INCAR (ADSORBED)

ISTART = 0
ICHARG = 2
ISPIN = 2
GGA = PE ##I have changed this for RPBE
ENCUT = 400
MAGMOM = 29*0.0 1*1.0 3*0.0 2*1.0 5*0.0 81*0.0 2*0.0 6*0.0

ISMEAR = 0
SIGMA = 0.05

LDIPOL = .TRUE.
IDIPOL = 3

LREAL = AUTO

ALGO = NORMAL
EDIFF = 1E-5
NELMIN = 8
NELM = 250

EDIFFG = 1E-3
NSW = 400
IBRION = 1
POTIM = 0.2

LWAVE = .FALSE.
LCHARG = .FALSE.

LVDW = .TRUE.

NPAR = 2
NSIM = 2

LDAU = .TRUE.
LASPH = .TRUE.
LDAUL = 3 -1 -1 -1
LDAUU = 5.2 0.0 0.0 0.0
LDAUJ = 1.0 0.0 0.0 0.0

LMAXMIX = 4
LORBIT = 11


INCAR (surface):

ISTART = 0
ICHARG = 2
ISPIN = 2
GGA = PE
ENCUT = 400
MAGMOM = 29*0.0 1*1.0 3*0.0 2*1.0 5*0.0 79*0.0

ISMEAR = 0
SIGMA = 0.05

LDIPOL = .TRUE.
IDIPOL = 3

LREAL = AUTO

ALGO = NORMAL
EDIFF = 1E-5
NELMIN = 8
NELM = 250

EDIFFG = 1E-3
NSW = 400
IBRION = 1
POTIM = 0.2

LWAVE = .FALSE.
LCHARG = .FALSE.

LVDW = .TRUE.

NPAR = 2
NSIM = 2

LDAU = .TRUE.
LASPH = .TRUE.
LDAUL = 3 -1
LDAUU = 5.2 0.0
LDAUJ = 1.0 0.0

LMAXMIX = 4
LORBIT = 11

Thanks in advance!

[support_vasp]

Hi,

We're sorry that we didn’t answer your question. This does not live up to the quality of support that we aim to provide. The team has since expanded. If we can still help with your problem, please ask again in a new post, linking to this one, and we will answer as quickly as possible.

Best wishes,

VASP