Dear Prof. Paolo,

Thank you for your prompt response.

I want to extract the Hamiltonian and eigenvectors (not necessarily Kohn-Sham, 
whatever eigenvectors QE solves for; I am aware that QE solves the Kohn-Sham 
equation, so I think it outputs the Kohn-Sham eigenvectors, please correct me 
if I am wrong).

The reasons for extracting the eigenvectors and the Hamiltonian are multiple. 
Primarily to calculate a couple of matrix elements for my research project. But 
I want to extract this data in a human-readable format so that I can get a 
better understanding of the QE DFT package as a whole.

Would the simple_output code provided by you in the post I linked earlier be 
the best way to go about doing this?

Pratyush Manocha
Graduate Student | M.S. Electrical & Computer Engineering
School of Electrical and Computer Engineering
Georgia Institute of Technology
From: Paolo Giannozzi <>
Sent: Monday, March 20, 2023 11:52
To: Quantum ESPRESSO users Forum <>
Cc: Manocha, Pratyush <>
Subject: Re: [QE-users] Best way to extract eigenvectors from pwscf output?

On 3/20/23 16:32, Manocha, Pratyush wrote:

>  I also saw a code posted by Prof. Paolo Giannozzi, which is not
> supposed to be used for anything greater than simple crystals

the first code (simple_output) can be used for large systems as well. It
will produce large files, though. The second code (simple_test) is
provided just as a test: it fills and diagonalizes a matrix containing
the hamiltonian in plane waves. This is possible only for small systems.
QE never fills the hamiltonian matrix.

> What would be the most robust way of extracting the
> Hamiltonian and eigenvectors of the Kohn-Sham equation in a
> human-readable format for such a large input cell size?

Once you have Kohn-Sham human-readable eigenvectors, what do you plan to
do: (human-)read all of them?

Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222
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