[Wien] Wavefunctions and System Hamiltonian

[Polatkan, Sascha]

Dear Mr. Blaha,


sorry for the delayed response, but I would like to pick this up again.

I do understand that the Hamiltonian is large and that I have to solve it for every k-point.

If I run a calculation, I end up typically with around 120 bands. Then, if I understand correctly,

I have to solve a 120x120 Hamiltonian for each k-point? That is feasible.


My end goal is simply to calculate things like Berry phases, optical conductivities, electron

densities, and energy bands myself. Also I want to understand the band couplings at arbitrary

k-points. I could visualize these if I had the H_ij(k).

You had mentioned that it is possible to print H_ij(k) (or hopefully save H_ij(k) to a file).


What I had originally intended is to obtain H_ij(k) from the electron density myself, once Wien2k

has finished a calculation, and thus finished approximating the electron density. To do this, it should

calculate some sum of basis functions. If I had the amplitudes for this sum, and the Hamiltonian as

a function of the density, I could set up very custom k-meshes, or recalculate bands on any

machine without access to Wien2k, or visualize different contributions to the energies like exchange

splittings or SOC resolved over k-space...or so I would think. I hope I'm not being naive here.


Trying to implement the latter paragraph is overkill and probably not too useful.

But if you could instruct me how to save the H_ij(k) to a file, that would be very helpful.  Can the

eigenvectors be saved too? They are saved in the case.vector files (I guess?), but these I cannot read.

I do understand that these files are massive, but I really would like to use them.


Kind regards,

SP.






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Previous messages are below:

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Message: 1
Date: Wed, 1 Jun 2022 12:22:11 +0000
From: "Polatkan, Sascha" <sascha.polatkan at pi1.uni-stuttgart.de>
To: "wien at zeus.theochem.tuwien.ac.at"
        <wien at zeus.theochem.tuwien.ac.at>
Subject: [Wien] Wavefunctions and System Hamiltonian
Message-ID: <451a1bb20bd04cfeb04509153b4a1d29 at pi1.uni-stuttgart.de>
Content-Type: text/plain; charset="iso-8859-1"

Greetings,

after I finished a calculation I would like to obtain the final wavefunctions of my system, and if possible, also the Hamiltonian.
I would like to do this, because I want to display system characteristics with my own code. Or maybe tweak something here and
there and observe what changes, to understand the system better. I'd like to have both k-space and real space representations.

If I understand right, I should be able to extract a list of spherical harmonics and interstitial orbitals for each atom, and constants
for weighting, which the Wien2k calculates for me.
The Hamiltonian should have a predefined set of elements from which I choose when I initialize the calculation. It should be obtainable
from the inputs already.
But I can't quite figure out how to get to the information. I hope you can help me out here.

Kind regards,
SP

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Message: 2
Date: Wed, 1 Jun 2022 20:24:51 +0200
From: Peter Blaha <pblaha at theochem.tuwien.ac.at>
To: wien at zeus.theochem.tuwien.ac.at
Subject: Re: [Wien] Wavefunctions and System Hamiltonian
Message-ID:
        <2bc0421b-1672-b6d5-d298-f3e109d45c8a at theochem.tuwien.ac.at>
Content-Type: text/plain; charset=UTF-8; format=flowed

Please remember: You get  number_of_k * number_of_bands "wavefunctions
in a solid". I.e. typically 1000-10000 wavefunctions.
So you need to know "which wf" you want to investigate in detail.

  Otherwise, please read my respond a couple of weeks ago about wave
functions.

> after I finished a calculation I would like to obtain the final
> wavefunctions of my system, and if possible, also the Hamiltonian.
> I would like to do this, because I want to display system
> characteristics with my own code. Or maybe?tweak?something here and
> there and observe what changes, to understand the system better. I'd
> like to have both k-space and real space representations.
>
> If I understand right, I should be able to extract a list of?spherical
> harmonics and interstitial orbitals for each atom, and constants
> for weighting, which the Wien2k?calculates for me.

--------------------------------------
I'm not sure how to understand this question. The Hamiltonian is kinetic
energy + eff.Potential.

Or do you mean the Hamilton matrix elements, H_ij(k). In principle you
can change the code and print this matrix. But the matrix is huge and
depends on k !

> The Hamiltonian should have a predefined set of elements from which I
> choose when I initialize the calculation. It should be obtainable
> from the inputs already.
> But I can't quite figure out how to get to?the information. I hope you
> can help me out here.
>
> Kind regards,
> SP

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