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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_______________________________________________
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]
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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/
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]
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