On 11/01/2024 20:06, Md. Jahid Hasan Sagor wrote:
Hi Dr. Paulatto,
Thank you so much for your suggestions. I was going in the wrong
direction. So if I use your recommended code
(https://anharmonic.github.io/thermal2/#d3_r2qx-code), would I be able
to generate the following figure for Bulk GaAs?
No. The anharmonic code is about vibrational properties.
Actually my main goal is to calculate dielectric function at different
temperatures (not 0 K).
You can try to do like in the paper. Or you can try a different
approach, i.e. replacing the sampling via molecular dynamics with a
stochastic sampling, like the one provided by the SSCHA code
http://sscha.eu/, which is also compatible with QE. Anyway, the
supercell they use is tiny (8 atoms, which is just the simple-cubic form
of GaAs), you should be able to use the epsilon.x code that comes with
QE (check the manual in PP/Doc/man_eps.pdf). I would say, start with
just epsilon as a function of the volume, test convergence and see if
you can afford it,.
kind regards
Thanks
Md Jahid Hasan
On Thu, Jan 11, 2024 at 9:19 AM Lorenzo Paulatto
<[email protected]> wrote:
Hello Jahid,
I have read the article very quickly, but I do not think they use
the RMS to compute epsilon. All they do is compute epsilon for a
few sample atomic potisions reached during the MD run, then they
average it. The "Theoretical Method" section does not have any
logic, but it is explained in the "Conclusions". The RMS seems to
be only used to ascertain the validity of the simulation.
hth
On 1/11/24 04:42, Md. Jahid Hasan Sagor wrote:
Hi Dr. Paulatto,
Thank you so much for your comments.
Actually, The paper (attached) extracted the temperature of each
configuration from the mean square displacement per atom of the
configuration (GaAs). In the harmonic approximation, they
determined the relationship between mean square displacement and
temperature T from the phonon density of states of bulk GaAs
calculated by Giannozzi et al. The equation as follows:
image.png
Here is the figure they generated
image.png
So, now If I can find out the RMS of GaAs using CPMD, I will try
to observe the corresponding configuration of GaAs atoms.
Finally, the atomic positions will be the input of Quantum
Espresso pw.x etc ( I mean normally how do we calculate
dielectric constant in QE).
Can I use it (
https://anharmonic.github.io/thermal2/#d3_r2qx-code) for the same
purpose?
Best
Hasan
On Wed, Jan 10, 2024 at 3:13 PM Lorenzo Paulatto
<[email protected]> wrote:
I would guess that you calculate the static dielectric
constant at the temperature-dependent volume (experimental,
or quasi-harmonic) and you are 90% of the way there. Do you
have a specific reason to believe that it would be
proportional to the RMS ?
Btw, the code d3_r2q.x included with the "anharmonic" package
can compute the RMS from an inexpensive phonon calculation,
maybe have a look at it before doing a large supercell MD.
https://anharmonic.github.io/thermal2/#d3_r2qx-code
cheers
On 10/01/2024 19:35, Md. Jahid Hasan Sagor wrote:
Actually, I have to calculate Dielectric constant for GaAs
for different temperatures (not 0 k). To do that, I need to
extract atomic positions for different RMS using CPMD. If
anyone know someone/ or give some guidelines, it would be
great help for me.
Thank you.
On Tue, Jan 9, 2024, 2:09 PM Md. Jahid Hasan Sagor
<[email protected]> wrote:
Dear QE community,
I want to calculate the mean square displacement of GaAs
using CPMD. From the mean square displacement, I want to
extract the configuration of atoms (e.g atomic position
of Ga and As). Could anyone please give me some
guidelines on how I can perform it? Should I use only
the cp.x package or by other means? Your time and
suggestions would be a great help for me.
Best Regards
Md Jahid Hasan
PhD Student, Mechanical Engineering
University of Maine
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Dr. Lorenzo Paulatto
IdR @ IMPMC - CNRS UMR 7590 & Sorbonne Université
phone: +33 (0)1 442 79822 / skype: paulatz
http://www.impmc.upmc.fr/~paulatto/ -
https://anharmonic.github.io/
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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
<http://www.max-centre.eu>)
users mailing list [email protected]
https://lists.quantum-espresso.org/mailman/listinfo/users
--
Dr. Lorenzo Paulatto
IdR @ IMPMC - CNRS UMR 7590 & Sorbonne Université
phone: +33 (0)1 442 79822 / skype: paulatz
http://www.impmc.upmc.fr/~paulatto/ - https://anharmonic.github.io/
23-24/423 B115, 4 place Jussieu 75252 Paris CX 05
--
Dr. Lorenzo Paulatto
IdR @ IMPMC - CNRS UMR 7590 & Sorbonne Université
phone: +33 (0)1 442 79822 / skype: paulatz
http://www.impmc.upmc.fr/~paulatto/ - https://anharmonic.github.io/
23-24/423 B115, 4 place Jussieu 75252 Paris CX 05
_______________________________________________
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 [email protected]
https://lists.quantum-espresso.org/mailman/listinfo/users
