[QE-users] It is neccesary to make a vc-relax in each DFT U+V calculation?
Giuseppe Mattioli
giuseppe.mattioli at ism.cnr.it
Mon Sep 30 16:18:56 CEST 2024
Dear Iurii
Is there any hope to have the ACBN0 pseudo-hybrid functional or its
adapted implementation by Lee and Son you mentioned soon available in
a regular QE version?
Thanks in advance
Giuseppe
Quoting Timrov Iurii <iurii.timrov at psi.ch>:
> Dear Robert,
>
> Originally, DFT+U and DFT+U+V were introduced to study
> transition-metal and rare-earth compounds. So usually, U has been
> applied to d and f electrons, and V for d-p and similar couples.
>
> In your system, you have only s and p electrons. Now there are more
> and more studies where U and V are applied to these electronic
> states (see e.g.
> https://journals.aps.org/prresearch/abstract/10.1103/PhysRevResearch.2.043410). I do not have much experience in using DFT+U and DFT+U+V with U and V from linear response for these systems. But I know that ACBN0 is used quite extensively for these systems and U and V are
> positive.
>
> HTH
>
> 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: ROBERT MIKHAIL GUZMAN ARELLANO <rguzmana at unmsm.edu.pe>
> Sent: Saturday, September 28, 2024 02:03
> To: Timrov Iurii <iurii.timrov at psi.ch>
> Cc: users at lists.quantum-espresso.org <users at lists.quantum-espresso.org>
> Subject: Re: [QE-users] It is neccesary to make a vc-relax in each
> DFT U+V calculation?
>
> Thanks a lot for your response.
>
> I was reading the paper that you recommended to me and I notice that
> your U and V values are positive.
>
> I am practicing the DFT U + V in graphane (graphene -C- completely
> hydrogenated - 4 atoms in the unit cell) with the objective to
> calculate U and V values of carbon and hydrogen orbitals or between
> them. I used the protocol of your paper and I am considering the HSE
> band structure calculation as a target, where the last gives a
> greater gap energy than the GGA DFT calculations.
>
> I obtained positive U values but the V values are negatives.
>
> These are:
>
> ATOMIC_SPECIES
> C 12.0107 C.pbe-n-kjpaw_psl.1.0.0.UPF
> H 1.008 H.pbe-kjpaw_psl.1.0.0.UPF
> ATOMIC_POSITIONS {angstrom}
> C 0.0000000000 0.0489411798 4.0736189551
> C 0.0000000000 1.5156118708 3.6147177498
> H 0.0000000000 0.0493473355 5.1835009290
> H 0.0000000000 1.5152618823 2.5048489230
> K_POINTS {automatic}
> 12 12 1 0 0 0
> HUBBARD ortho-atomic
> V C-2P C-2P 1 1 2.8212
> V C-2P C-2P 2 2 2.8212
> V C-2P H-1S 1 3 -0.0283
> V C-2P H-1S 2 4 -0.0283
> V C-2P C-2P 1 2 -0.1355
> V H-1S H-1S 3 3 4.3467
> V H-1S H-1S 4 4 4.3467
>
> So I am wondering what is the criteria to validate or accept a
> negative V, and another question is which orbitals need to be
> selected for a V and U calculations. For example in the commented
> paper, the Mn-3d and O-2p orbitals are considered but avoided the
> others valence orbitals. I am thinking that the most energetic
> orbitals of each atom must be considered... Could you recommend
> another work where discuss it ?
>
> Thanks for the attention!!
>
>
>
> El vie, 27 sept 2024 a las 3:01, Timrov Iurii
> (<iurii.timrov at psi.ch<mailto:iurii.timrov at psi.ch>>) escribió:
> 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<mailto:users-bounces at lists.quantum-espresso.org>> on behalf of ROBERT MIKHAIL GUZMAN ARELLANO via users
> <users at lists.quantum-espresso.org<mailto:users at lists.quantum-espresso.org>>
> Sent: Thursday, September 26, 2024 17:34
> To:
> users at lists.quantum-espresso.org<mailto:users at lists.quantum-espresso.org>
> <users at lists.quantum-espresso.org<mailto: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.
GIUSEPPE MATTIOLI
CNR - ISTITUTO DI STRUTTURA DELLA MATERIA
Via Salaria Km 29,300 - C.P. 10
I-00015 - Monterotondo Scalo (RM)
Mob (*preferred*) +39 373 7305625
Tel + 39 06 90672342 - Fax +39 06 90672316
E-mail: <giuseppe.mattioli at ism.cnr.it>
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