[Pw_forum] kohen -sham orbitals ortogonality and ortonormality

[Alexey Akimov]

Dear Fariba,

The Kohn-Sham (please, not kohen) orbitals produced by pp.x are not orthonormalized in general, because of the pseudo-potentials and projection techniques (PAW). However, practically,  you may safely assume they are orthogonal and almost normalized (self-overlaps are not far from 1.0). This is especially true for norm-conserving PP (by construction, the wavefunctions supposed to preserve norm), and, in slightly smaller extent, for ultra-soft pseudopotentials. For PAW wavefunctions the trick is to reconstruct full wavefunction from the projection, so it is S|psi>. If i remember it correctly, the ortogonality will then be for <psi_i|S|psi_j> = delta_ij. However you can obtain S|psi> with pp.x as well as |psi>. 
Please anyone correct me if i'm wrong at some point.

Thank you,
Alexey

----- Original Message -----
From: nazari at iasbs.ac.ir
To: "PWSCF Forum" <pw_forum at pwscf.org>
Sent: Tuesday, August 28, 2012 6:23:31 AM
Subject: [Pw_forum] kohen -sham orbitals ortogonality and ortonormality




Dear All, 

Would you please let me know if the kohen -sham orbitals ,which are obtained by pp.x, are normalized, orthogonalized or orthonormalized? 

Regards 
Fariba Nazari 
IASBS 
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-- 
Dr. Alexey V. Akimov

Postdoctoral Research Associate
Department of Chemistry
University of Rochester

aakimov at z.rochester.edu