My Community

Dear VASP useres,

I'm trying to calculate the (100) surface energy of of ThO2 using slab models. Since the (100) layers are charged (alternating Th and O planes), there is a net dipole moment perpendicular to the slab (z-direction). In order include the dipole corrections for the total energy I set IDIPOL = 3 and carried out the calculations on slabs with increasing thickness. For thin slabs the dipole corrections seem to be reasonable (dipol+quadrupol energy correction 0.246832 eV), but for thicker slabs the corrections jump to unreasonably large values: dipol+quadrupol energy correction 179.223968 eV.
I browsed the forum and the user manual, but I couldn't find an explanation for this behaviour. I would appreciate if somebody could help me with this issue.

Here is my INCAR:

System = ThO2_slab
ISTART = 1
ICHARG = 1
ENCUT = 500
PREC = High

ISPIN = 1
ISMEAR = 0; SIGMA = 0.01
LORBIT = 11

NSW = 60
ISIF = 2
IBRION = 1
EDIFFG = -0.01

LMAXMIX = 6

IDIPOL = 3

and the OUTCAR:

DIPCOR: dipole corrections for dipol
direction 3 min pos 92,
dipolmoment 0.000000 0.000000 31.340853 electrons x Angstroem
Tr[quadrupol] -1676.729050

energy correction for charged system 0.000000 eV
dipol+quadrupol energy correction 179.223968 eV
added-field ion interaction 0.000000 eV (added to PSCEN)


Thank you,
Zsolt

please check if the origin of the dipol was kept at reasonable positions for all test you made. Of course the dipol moment increases with increasing slab thickness,