[QE-users] It is neccesary to make a vc-relax in each DFT U+V calculation?

[Timrov Iurii]

Dear Robert,

Please have a look at this paper: https://journals.aps.org/prb/abstract/10.1103/PhysRevB.103.045141

Yes, generally, one should also redo the vc-relax calculations using updated U and V values using DFT+U+V. But if, for example, one wants to work with the fixed geometry (e.g. the experimental one), then obviously there is no need to do the vc-relax calculations.

Greetings,
Iurii

----------------------------------------------------------
Dr. Iurii TIMROV
Tenure-track scientist
Laboratory for Materials Simulations (LMS)
Paul Scherrer Institut (PSI)
CH-5232 Villigen, Switzerland
+41 56 310 62 14
https://www.psi.ch/en/lms/people/iurii-timrov
________________________________
From: users <users-bounces at lists.quantum-espresso.org> on behalf of ROBERT MIKHAIL GUZMAN ARELLANO via users <users at lists.quantum-espresso.org>
Sent: Thursday, September 26, 2024 17:34
To: users at lists.quantum-espresso.org <users at lists.quantum-espresso.org>
Subject: [QE-users] It is neccesary to make a vc-relax in each DFT U+V calculation?

Dear members,

I am starting to work in DFT U+V making calculations with pw.x and hp.x of Quantum Espresso package. So my question is:

In order to calculate the U and V values with hp.x. What is the path to follow?

At his time. I am doing these steps.

0. Calibrate pseudo potentials, k-points, and frequency of waves and density.

1. Calculate the crystalline structure using vc-relax.

2. Make a scf calculation using the best atomic positions and unit cell parameters obtained in vc-relax calculation. In this calculation, I put a small value of U and V between orbitals. (1.d-3 eV)

3 run hp.x in order to calculate better values of U and V.

4 extract the U and V values calculated by hp.x, and put these in a new scf calculation and run the last.

5 repeat the 3 step and after the 4 step until the U and V values between 2 different calculations look equal or with small difference (0.01eV).

My Question is: is it necessary to make a vc-relax between the 3 and 4 steps? I looked at some examples which do that  in order to calculate U value,but do not do the same when calculating V (interaction between different orbitals).

During this month I have been working with atoms whose valence orbitals are S and P, and I understand that for these orbitals, not being very localized like the D orbitals, it is necessary to work with U and V, where V responds to the coulomb interaction between orbitals of neighboring atoms.

Thank's for your attention.

Best regards.
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