Hi Jayraj,
you wrote several times, but probably many did not know where to start -
because you are addressing several complex problems without seeming to
have much background in the field. Answers to your 3 points:
1) you will not get anything meaningul with the low cutoffs you suggest,
just random stuff. use the minimum cutoffs suggested in my point 2) here
below.
2) not sure - pseudopotentials are like people, they can be messed up
deep inside. use the SSSP 1.3 efficiency:
https://www.materialscloud.org/discover/sssp/table/efficiency
3) not sure where to start - you need to learn and understand MD - a
good start is if you google "ercolessi md primer"
nicola
On 18/10/2023 11:18, Jayraj Anadani wrote:
Hello, QE community!
On my metallic system, which has 128 atoms, I am running AIMD
calculations using the pw.x code. Two pseudopotentials, PAW and USPP,
were each tested individually. I have the following queries:
1. For a faster AIMD calculation at a specific temperature, *Can I
perform the whole simulation with a very low "ecutwfc" and
"conv_thr" (i.e. ecutwfc=5 or 10) below a minimum cutoff of
pseudopotential? *So that I can get the next ionic position very
quickly with a fast scf cycle, then at the last MD step I will
perform a single point energy (SCF) calculation with high "ecutwfc"
and "conv_thr" to maintain a good amount of accuracy.
2. Compared to PAW pseudopotential, USPP's convergence occurs *much
more quickly. why*? (when ecutwfc is 25)
3. The temperature fluctuation is incredibly small and nearly equal in
the MD simulation of thousands of atoms in LAMMPS at a specific
temperature (i.e., 1000K). However, the temperature fluctuation in
MD with pw.x (AIMD) is significant, so we must set "tolp" which
stands for tolerance for velocity rescaling. Although the average
temperature is kept constant, *how closely does this significant
fluctuation match the LAMMPS MD simulation?*
Thank you
regards
JAYRAJ ANADANI
Department of Physics
SPU Research scholar
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Prof Nicola Marzari, Chair of Theory and Simulation of Materials, EPFL
Director, National Centre for Competence in Research NCCR MARVEL, SNSF
Head, Laboratory for Materials Simulations, Paul Scherrer Institut
Contact info and websites at http://theossrv1.epfl.ch/Main/Contact
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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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