[DFTB-Plus-User] comparison of hamsqr1.dat, oversqr1.dat and band.dat

[James A Charles]

Hi,


Thanks a lot for the confirmation. After checking closer, I was using the unrelaxed positions when doing the restart. (My script didn't do the substitution I thought it did). Now they both match.


Thanks for your help,

James

________________________________
From: DFTB-Plus-User <dftb-plus-user-bounces at mailman.zfn.uni-bremen.de> on behalf of Bálint Aradi <aradi at uni-bremen.de>
Sent: Thursday, May 17, 2018 5:29:26 AM
To: dftb-plus-user at mailman.zfn.uni-bremen.de
Subject: Re: [DFTB-Plus-User] comparison of hamsqr1.dat, oversqr1.dat and band.dat

>
> I am trying to compare the H and S from the hamsqr1.dat and oversqr.dat
> for the Gamma point and noticing that the eigenvalues given in band.dat
> do not correspond to the eigenvalues I get from solving hamsqr1.dat and
> oversqr.dat in MATLAB. Am I missing something? Or should these both match?

Yes, they should match. Please keep in mind, though, that with WriteHS =
Yes, DFTB+ would only builds the Hamiltonian and quits then immediately,
so that no SCC-cycles are done. If you want to get the Hamiltonian for a
fully converged SCC-calculation, then

* Run the SCC-calculation normally

* Start a follow-up calculation with ReadInitialCharges = Yes and
WriteHS = Yes.

Diagonalizing the hamsqr1.dat and oversqr.dat files you obtained this
way, should reproduce the eigenvalues you got with the SCC-calculation.

I've just tried it for H2O with the following Python-snippet, and it
seems to work. ;-)

import numpy as np
import scipy.linalg as linalg

over = np.loadtxt('oversqr.dat', skiprows=5)
ham = np.loadtxt('hamsqr1.dat', skiprows=5)

eigvals, eigvecs = linalg.eigh(ham, over)
print(eigvals)

Best regards,

Bálint


--
Dr. Bálint Aradi
Bremen Center for Computational Materials Science, University of Bremen
http://www.bccms.uni-bremen.de/cms/people/b-aradi/

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