Electric field and dipole correction

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Electric field

A saw-like potential simulating an electric field is added to the bare ionic potential.

INPUT_PARAMETERS
efield_flag        1
dip_cor_flag       0
efield_dir         2
efield_pos_max     0.5
efield_pos_dec     0.1
efield_amp         0.001

• efield_flag : If set to true, a saw-like potential simulating an electric field is added to the bare ionic potential.
• dipcorflag : If dip_cor_flag == true and efield_flag == true, a dipole correction is also added to the bare ionic potential. If you want no electric field, efield_amp should be zero. Must be used ONLY in a slab geometry for surface calculations, with the discontinuity FALLING IN THE EMPTY SPACE.
• efielddir : The direction of the electric field or dipole correction is parallel to the reciprocal lattice vector, so the potential is constant in planes defined by FFT grid points, efielddir = 0, 1 or 2. Used only if efield_flag == true.
• efieldposmax : Position of the maximum of the saw-like potential along crystal axis efield_dir, within the unit cell, 0 < efield_pos_max < 1. Used only if efield_flag == true.
• efieldposdec : Zone in the unit cell where the saw-like potential decreases, 0 < efield_pos_dec < 1. Used only if efield_flag == true.
• efield_amp : Amplitude of the electric field, in Hartree a.u.; 1 a.u. = 51.4220632*10^10 V/m. Used only if efield_flag == true. The saw-like potential increases with slope efield_amp in the region from (efield_pos_max+efield_pos_dec-1) to (efield_pos_max), then decreases until (efield_pos_max+efield_pos_dec), in units of the crystal vector efield_dir. Important: the change of slope of this potential must be located in the empty region, or else unphysical forces will result.

Dipole correction

A dipole correction is added to the bare ionic potential.Must be used ONLY in a slab geometry, for surface calculations, with the discontinuity FALLING IN THE EMPTY SPACE.

INPUT_PARAMETERS
efield_flag        1
dip_cor_flag       1
efield_dir         2
efield_pos_max     0.5
efield_pos_dec     0.1
efield_amp         0

Note: efield_amp must be zero so that there is no electric field.

Electric field and Dipole correction

Both external electric field and dipole correction are added to the bare ionic potential.

INPUT_PARAMETERS
efield_flag        1
dip_cor_flag       1
efield_dir         2
efield_pos_max     0.5
efield_pos_dec     0.1
efield_amp         0.001

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