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LDIPOL

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LDIPOL = .TRUE. | .FALSE.
Default: LDIPOL = .FALSE. 

Description: LDIPOL switches on corrections to the potential and forces in VASP. Can be applied for charged molecules and molecules and slabs with a net dipole moment.


Due to the periodic boundary conditions, not only the total energy converges slowly with respect to the size of the supercell, but also the potential and the forces are affected by finite size errors. This effect can be counterbalanced by setting LDIPOL=.TRUE. in the INCAR file. For LDIPOL=.TRUE.,a linear correction and for charged cells a quadratic electrostatic potential is added to the local potential in order to correct the errors introduced by the periodic boundary conditions. This is in the spirit of Neugebauer et al.[1] (but more general and the total energy is correctly implemented, whereas the Neugebauer paper contains an erroneous factor 2 in the total energy). The biggest advantage of this mode is that leading errors in the forces are corrected, and that the work-function can be evaluated for asymmetric slabs. The disadvantage is that the convergence to the electronic groundstate might slow down considerably (i.e., more electronic iterations might be required to obtain the required precision). It is recommended to use this mode only after pre-converging the orbitals without the LDIPOL flag, and the center of charge should be set in the INCAR file (DIPOL= center of mass). The user must also ensure that the cell is sufficiently large to determine the dipole moment with sufficient accuracy. If the cell is too small, charge might slash through the vacuum, causing very slow convergence (often convergence improves with the size of the supercell).

Restrictions: for charged systems, the potential correction is currently only implemented for cubic supercells. VASP will stop if the supercell is not cubic and LDIPOL=.TRUE.

Related Tags and Sections

Monopole Dipole and Quadrupole corrections, NELECT, EPSILON, IDIPOL, DIPOL, LMONO, EFIELD

Examples that use this tag

References

  1. J. Neugebauer and M. Scheffler, Phys. Rev. B 46, 16067 (1992).