Electrostatic corrections
For charged cells or for calculations of molecules and surfaces with a large dipole moment, the energy converges very slowly with respect to the size of the supercell. Using methods discussed by Makov et al.[1] and Neugebauer et al.[2], VASP can correct for the leading errors (in many details, we have taken a more general approach, though).
Summary of relevant INCAR tags
This section contains a summary of all the INCAR tags that are currently implemented for performing monopole, dipole and quadrupole corrections using VASP. Please see the relevant pages of the respective tags for more detailed information.
| Dimensionality of the system | Does the system have net charge? | Does the system have a net dipole moment? | Relevant INCAR tags for monopole/dipole corrections |
| 3D | No | No | None |
| 3D | Yes | No | NELECT, LMONO, EPSILON |
| 3D | No | Yes | DIPOL, IDIPOL, EPSILON |
| 3D | Yes | Yes | NELECT, DIPOL, IDIPOL, EPSILON |
| 2D | No | No | None |
| 2D | Yes | No | NELECT |
| 2D | No | Yes | IDIPOL, LDIPOL, DIPOL |
| 2D | Yes | Yes | NELECT |
| 1D | No | No | None |
| 1D | Yes | No | NELECT |
| 1D | No | Yes | Not implemented |
| 1D | Yes | Yes | Not implemented |
| 0D | No | No | None |
| 0D | Yes | No | NELECT, LMONO, LDIPOL |
| 0D | No | Yes | LDIPOL |
| 0D | Yes | Yes | NELECT, LMONO, LDIPOL |
| Tip: If an external electrostatic field is desired for slab, or molecular calculations, see EFIELD |
Current limitations
For the current implementation, there are several restrictions; please read carefully:
- Charged systems:
- Quadrupole corrections are only correct for cubic supercells (this means that the calculated 1/L3 corrections are wrong for charged supercells if the supercell is non-cubic). In addition, we have found empirically that for charged systems with excess electrons (NELECT>NELECTneutral) more reliable results can be obtained if the energy after correction of the linear error (1/L) is plotted against 1/L3 to extrapolate results manually for L→∞. This is due to the uncertainties in extracting the quadrupole moment of systems with excess electrons.
- Potential corrections are only possible for orthorhombic cells (at least the direction in which the potential is corrected must be orthogonal to the other two directions).
Related Tags and Sections
NELECT, EPSILON, DIPOL, IDIPOL, LDIPOL, LMONO, EFIELD