<div dir="ltr"><div dir="auto"><div>Thank you Nicola sir for your reply, and sorry for repeating the message.</div><div dir="auto"><br></div><div dir="auto">Actually, I am trying to obtain the metallic glass configuration through AIMD using the pw.x code. My system has 128 atoms of Zr and Cu.</div><div><ul><li><b>VASP procedure:</b> first melted at 3000K using a nose thermostat up to 5 picoseconds, then quenched at a high cooling rate of 10e13 K/s and reached 300K temperature.</li><li><b>For the Quantum Espresso procedure,</b> I already used the cp.x code with the nose-hoover thermostat, but due to the metallic nature of Zr and Cu, I couldn't control the electron's adiabaticity. and if I perform the CG method in cp.x code, that will take too much time because of my computational limitations. So I prefer MD simulation using pw.x with "david" diagonalization. As the nose thermostat is not available in pw. x code, so I am using a "rescaling" thermostat for melting and "reduce-T" for quenching. However, the temperature fluctuations are too high compared to the other literature.</li></ul></div><div>regards</div><div>jayraj</div><div dir="auto"><br><div class="gmail_quote" dir="auto"><div dir="ltr" class="gmail_attr">On Wed, 18 Oct, 2023, 5:41 pm Nicola Marzari via users, <<a href="mailto:users@lists.quantum-espresso.org" target="_blank">users@lists.quantum-espresso.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><br>
Hi Jayraj,<br>
<br>
you wrote several times, but probably many did not know where to start - <br>
because you are addressing several complex problems without seeming to <br>
have much background in the field. Answers to your 3 points:<br>
<br>
1) you will not get anything meaningul with the low cutoffs you suggest, <br>
just random stuff. use the minimum cutoffs suggested in my point 2) here <br>
below.<br>
<br>
2) not sure - pseudopotentials are like people, they can be messed up <br>
deep inside. use the SSSP 1.3 efficiency: <br>
<a href="https://www.materialscloud.org/discover/sssp/table/efficiency" rel="noreferrer noreferrer" target="_blank">https://www.materialscloud.org/discover/sssp/table/efficiency</a><br>
<br>
3) not sure where to start - you need to learn and understand MD - a <br>
good start is if you google "ercolessi md primer"<br>
<br>
nicola<br>
<br>
<br>
<br>
<br>
On 18/10/2023 11:18, Jayraj Anadani wrote:<br>
> Hello, QE community!<br>
> On my metallic system, which has 128 atoms, I am running AIMD <br>
> calculations using the pw.x code. Two pseudopotentials, PAW and USPP, <br>
> were each tested individually. I have the following queries:<br>
> <br>
> 1. For a faster AIMD calculation at a specific temperature, *Can I<br>
> perform the whole simulation with a very low "ecutwfc" and<br>
> "conv_thr" (i.e. ecutwfc=5 or 10) below a minimum cutoff of<br>
> pseudopotential? *So that I can get the next ionic position very<br>
> quickly with a fast scf cycle, then at the last MD step I will<br>
> perform a single point energy (SCF) calculation with high "ecutwfc"<br>
> and "conv_thr" to maintain a good amount of accuracy.<br>
> 2. Compared to PAW pseudopotential, USPP's convergence occurs *much<br>
> more quickly. why*? (when ecutwfc is 25)<br>
> 3. The temperature fluctuation is incredibly small and nearly equal in<br>
> the MD simulation of thousands of atoms in LAMMPS at a specific<br>
> temperature (i.e., 1000K). However, the temperature fluctuation in<br>
> MD with pw.x (AIMD) is significant, so we must set "tolp" which<br>
> stands for tolerance for velocity rescaling. Although the average<br>
> temperature is kept constant, *how closely does this significant<br>
> fluctuation match the LAMMPS MD simulation?*<br>
> <br>
> Thank you<br>
> <br>
> regards<br>
> JAYRAJ ANADANI<br>
> Department of Physics<br>
> SPU Research scholar<br>
> <br>
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<br>
-- <br>
----------------------------------------------------------------------<br>
Prof Nicola Marzari, Chair of Theory and Simulation of Materials, EPFL<br>
Director, National Centre for Competence in Research NCCR MARVEL, SNSF<br>
Head, Laboratory for Materials Simulations, Paul Scherrer Institut<br>
Contact info and websites at <a href="http://theossrv1.epfl.ch/Main/Contact" rel="noreferrer noreferrer" target="_blank">http://theossrv1.epfl.ch/Main/Contact</a><br>
<br>
_______________________________________________<br>
The Quantum ESPRESSO community stands by the Ukrainian<br>
people and expresses its concerns about the devastating<br>
effects that the Russian military offensive has on their<br>
country and on the free and peaceful scientific, cultural,<br>
and economic cooperation amongst peoples<br>
_______________________________________________<br>
Quantum ESPRESSO is supported by MaX (<a href="http://www.max-centre.eu" rel="noreferrer noreferrer" target="_blank">www.max-centre.eu</a>)<br>
users mailing list <a href="mailto:users@lists.quantum-espresso.org" rel="noreferrer" target="_blank">users@lists.quantum-espresso.org</a><br>
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