[QE-users] Last SCF step of a vc-relax job in DFT+U

[Iurii TIMROV]

> What are the advantages of this choice?


Without this "trick", for some systems the final SCF calculation might not converge to the same ground state as in the vc-relax run.


Iurii


--
Dr. Iurii TIMROV
Senior Research Scientist
Theory and Simulation of Materials (THEOS)
Swiss Federal Institute of Technology Lausanne (EPFL)
CH-1015 Lausanne, Switzerland
+41 21 69 34 881
http://people.epfl.ch/265334
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From: users <users-bounces at lists.quantum-espresso.org> on behalf of Mahmoud Payami Shabestari <mpayami at aeoi.org.ir>
Sent: Wednesday, November 30, 2022 9:19:52 PM
To: Quantum ESPRESSO users Forum
Subject: Re: [QE-users] Last SCF step of a vc-relax job in DFT+U

I found the following statement in release-notes:

New in 6.7 version:
  * In vc-relax with Hubbard corrections, the final SCF calculation is done by
    reading atomic occupations from file produced during the vc-relax
    (rather than recomputing them from scratch).

What are the advantages of this choice? Does it inform about possible transition among metastable states?

Mahmoud
From: "Mahmoud Payami Shabestari" <mpayami at aeoi.org.ir>
To: "users at lists.quantum-espresso.org" <users at lists.quantum-espresso.org>
Date: Wed, 30 Nov 2022 10:49:09 +0330
Subject: [QE-users] Last SCF step of a vc-relax job in DFT+U

Dear All,
Hi.

As far as I know from, in a vc-relax job for a normal system, when the calculated pressure in the last scf (which starts with optimized lattice parameters and atomic positions, while keeping other input values fixed) is much higher than default 0.5kbar value, it implies that one has to increase ecutwfc, ecutrho, ... until this large difference disappears.
In a DFT+U run, I encountered such a problem. But when I performed a separate scf but with optimized cell parameters and atomic positions, I get the optimized value for pressure say 0.01 kbar, which is perfect. I am using QE-7.1.
Does it mean that in the last scf run of vc-relax the diagonalised ocuupation matrices are used instead of the values specified in the input?
Thanks in advance.

Best regards,
Mahmoud Payami
NSTRI, AEOI, Tehran, Iran

Email: mpayami at aeoi.org.ir
Phone: +98 (0)21 82066504
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