Dear Minoru,
Thank you very much for taking the time to explain these examples in
detail. If you don't mind I have a few followup questions:
1) for the first case, the ESM calculation: how does one determine the
vacuum region? In a regular slab calculation, as far as my understanding
goes, one increases the vacuum region until there is little interaction
between the periodical neighbors as it were. In this case, I have
performed two calculations for 10 A of vacuum on either side of the slab
and then for 5 A. The latter case had a lower total energy than the
former. Is this normal? I have also tried a rather large 30 A on either
side, but the calculation failed to converge.
2) also for the ESM case: do I understand correctly that for the
metal-slab-metal case, one controls the Hartree potential using
esm_efield and for the vacuum-slab-metal case one uses the tot_charge
parameter?
I am trying to make that the Hartree potential for my slab with
ferroelectric layers is correct as the following article suggests:
https://www.nature.com/articles/s41524-021-00529-1
They are using a different method and I believe that a combination of
ESM and FCP could accomplish the same result for my case. That is why my
next question is regarding FCP:
3) in FCP one has to provide the target_mu. In your example you use the
Fermi level from the ESM calculation in the first example as the target
mu in the FCP calculation. Is this the route that must be used?
Thank you again for your time!
Best regards,
Lucian
On 11/04/2022 16:16, Otani Minoru wrote:
Dear Lucian,
I made those examples in PW/examples/ESM_example directory. Here, I am
going to explain the purpose of each examples.
1) ESM
One can understand the overall usage of the effective screening medium
(ESM) method. More precisely, when you plot the esm1 file, you can see
the difference of the calculated electrostatic potentials depending on
the boundary conditions, i.e., pbc, bc1, bc2, and bc3. By changing the
parameter "tot_charge", you can see how the Fermi energy changes in a
Constant-N calculation: Constant-N means that we fix the total number
of electron (N) during the SCF calculation. If you want to understand
more detail about the method and configuration of the slab model,
please read the original paper:
Physical Review B 73, 115407 (2006)
2) FCP & 3) GCSCF
Unlike the Constant-N calculation, the second (FCP) and the third
(GCSCF) examples, we can conduct an electronic structure calculation
with fixed chemical potential for electron (constant-mu). FCP stands
for fictitious charge particle and the original paper is the following:
Physical Review Letters 109, 266101 (2012).
GCSCF is the abbreviation for the grand canonical SCF and the original
paper is below:
J. Chem. Phys. 146, 114104 (2017).
You can find the difference between FCP and GCSCF calculations in the
following paper:
Physical Review Materials 5, 065001 (2021).
As stated in the paper, FCP and GCSCF have their advantages in the
constant-mu calculations. Thus we have implemented both methods for
users convenience.
Best regards,
Minoru
--------------------------------------------------------------------------------------------------------
Minoru Otani, Ph.D., Professor
Center for Computational Sciences and Faculty of Pure and Applied
Sciences,
University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, Japan
TEL: +81-29-853-4273
FAX: +81-29-853-6406
E-mail: ot...@ccs.tsukuba.ac.jp <mailto:ot...@ccs.tsukuba.ac.jp>
Web: https://www2.ccs.tsukuba.ac.jp/public/otani/
--------------------------------------------------------------------------------------------------------
On Apr 11, 2022, at 15:48, Lucian D. Filip <lucian.fi...@infim.ro> wrote:
Hello all,
Is there a tutorial out there that explains in detail how to use the
FCP method? I have read the one in the PW/examples on github but I
can't figure out what it is trying to accomplish.
It is split into three types of calculations: 1) ESM calculation; 2)
FCP calculation; 3) GCSCP calculation. Why is that? Are they related?
Is this the order one is supposed to use to obtain a what exactly?
Can someone explain the purpose of each steps taken in this example?
Thank you!
Lucian
--
Dr. Lucian Dragos Filip
National Institute of Materials Physics
Atomistilor str. 405A
PO Box MG. 7
Magurele, 077125
Bucharest, Romania
E-mail: lucian.fi...@infim.ro <mailto:lucian.fi...@infim.ro>
Website: http://lucianfilip.wordpress.com
_______________________________________________
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country and on the free and peaceful scientific, cultural,
and economic cooperation amongst peoples
_______________________________________________
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_______________________________________________
The Quantum ESPRESSO community stands by the Ukrainian
people and expresses its concerns about the devastating
effects that the Russian military offensive has on their
country and on the free and peaceful scientific, cultural,
and economic cooperation amongst peoples
_______________________________________________
Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
users mailing listus...@lists.quantum-espresso.org
https://lists.quantum-espresso.org/mailman/listinfo/users
--
Dr. Lucian Dragos Filip
National Institute of Materials Physics
Atomistilor str. 405A
PO Box MG. 7
Magurele, 077125
Bucharest, Romania
E-mail:lucian.fi...@infim.ro
Website:http://lucianfilip.wordpress.com
_______________________________________________
The Quantum ESPRESSO community stands by the Ukrainian
people and expresses its concerns about the devastating
effects that the Russian military offensive has on their
country and on the free and peaceful scientific, cultural,
and economic cooperation amongst peoples
_______________________________________________
Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
users mailing list users@lists.quantum-espresso.org
https://lists.quantum-espresso.org/mailman/listinfo/users
