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

[Anders Hellman]

Hi Jussi,

Thank you for your quick replay. 

On Oct 4, 2011, at 8:33 AM, Jussi Enkovaara wrote:

> 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)
> 

Thanks, I will try this. The reason for my confusion is that I always thought that at the Gamma point the wavefuncton is real, no matter if I have several of k-points. 



>> 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.

That is what I suspected. However, can I extract the electrostatic (Hartree) potential alone somehow? Perhaps a simple modification in the .get_effective_potential().

Cheers,
Anders