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LCALCPOL = .TRUE. | .FALSE.
Default: LCALCPOL = .FALSE.
Description: LCALCPOL=.TRUE. switches on the evaluation of the Berry phase expressions for the macroscopic electronic polarization in accordance with the so-called Modern Theory of Polarization.
For LCALCPOL=.TRUE., VASP calculates the electronic contribution to the polarization, along the three reciprocal lattice vectors Gi, i=1,2,3, (i.e. Σi P·Gi) in a single run (unlike LBERRY=.TRUE.).
An example: The fluorine displacement dipole (Born effective charge) in NaF
- With INCAR file:
- KPOINTS file:
6x6x6 0 Gamma 6 6 6 0 0 0
- POSCAR file:
NaF 4.5102 0.0 0.5 0.5 0.5 0.0 0.5 0.5 0.5 0.0 1 1 Direct 0.0000000000000000 0.0000000000000000 0.0000000000000000 0.5000000000000000 0.5000000000000000 0.5000000000000000
- and LDA Na_sv and F PAW datasets.
The OUTCAR file should now contain the following lines:
Ionic dipole moment: p[ion]=( 2.25510 2.25510 2.25510 ) electrons Angst Total electronic dipole moment: p[elc]=( 0.00000 0.00000 0.00000 ) electrons Angst
To calculate the change in the electronic polarization of NaF due to the displacement of the fluorine sublattice we repeat the previous calculation with the following POSCAR file:
NaF 4.5102 0.0 0.5 0.5 0.5 0.0 0.5 0.5 0.5 0.0 1 1 Direct 0.0000000000000000 0.0000000000000000 0.0000000000000000 0.5100000000000000 0.5100000000000000 0.4900000000000000
The OUTCAR should now contain something very similar to the following lines:
Ionic dipole moment: p[ion]=( 2.25510 2.25510 1.93939 ) electrons Angst Total electronic dipole moment: p[elc]=( 0.00000 0.00000 0.36061 ) electrons Angst
From the above one easily recognizes that the change in the electronic dipole moment due to the F-sublattice displacement is:
and the corresponding change in the ionic dipole moment:
Thus the total change is found to be:
and considering that the F-sublattice was displaced by 0.045102 Å these calculations yield a Born effective charge for fluorine of
The socalled parallel or direction in the integration over the reciprocal space unit cell is set in IGPAR.