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 <[email protected]>:
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 <[email protected]>
Sent: Saturday, September 28, 2024 02:03
To: Timrov Iurii <[email protected]>
Cc: [email protected] <[email protected]>
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
(<[email protected]<mailto:[email protected]>>) 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
<[email protected]<mailto:[email protected]>> on behalf of ROBERT MIKHAIL GUZMAN ARELLANO via users
<[email protected]<mailto:[email protected]>>
Sent: Thursday, September 26, 2024 17:34
To:
[email protected]<mailto:[email protected]>
<[email protected]<mailto:[email protected]>>
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: <[email protected]>
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