[gpaw-users] Positive and negative part of the wavefunction + electrostatic potential

[Jussi Enkovaara]

Hi Anders,

On 2011-10-03 22:45, Anders Hellman wrote:
> Dear GPAW users,
>
> I have two problems that I would be grateful if someone could help me with.
>
> 1) I am interested in plotting the wave function of a slab (calculated with a number of kpoints). However, when I follow the CO example I lose the negative sign of the wave function, even when I ask for the get_psuedo_wave_function in in kpt=0. What am I doing wrong?

With k-points, your wave functions are complex. Neither .cube or .plt formats 
support complex valued data, so when writing the wave function data to file
(e.g. write(fname, atoms, data=wf) in the CO example), the absolute value of wave 
function is taken and written. If you want to plot both the real and imaginary part 
of the wave function, you can try something like:

wf = calc.get_pseudo_wave_function(band=0, kpt=0)
write('wf_real.cube', atoms, data=wf.real)
write('wf_imag.cube', atoms, data=wf.imag)

> 2) Will the get_effective_potential() give me the electrostatic potential in my slab or what does this give me?

"get_effective_potential" gives the smooth part of the Kohn-Sham effective 
potential, i.e. it contains electrostatic (Hartree) potential and 
exchange-correlation potential. In PAW formalism also so called zero potential 
(vbar) enters
the smooth effective potential. You can look e.g. equations in (30)-(32) in
J. Phys.: Condens. Matter 22, 253202 (2010)
for more detailed information about terms entering effective
potential (\tilde{v}) in GPAW.

Best regards,
Jussi