[QE-users] 回复: Pw.x Cell_factor issue

[Lorenzo Paulatto]

Hello,

for molecules, like your Li2S6, you cannot do vc-relax, because it would 
produce a Li2S6 solid crystal. Plane waves are always periodic, so you 
need some vacuum around to keep images isolated. What you should do, is 
check the convergence with the amount of vacuum to ensure that there is 
no sizeable interaction between the periodic copies (and/or use some 
kind of correction for isolated systems).

For 2D systems, i.e. graphene + any kind of rubbish, you can use 
vc-relax, but you have to specify an appropriate "cell_dofree" to ensure 
that the amount of vacuum in the out-of-plane direction is preserved. 
Again, you should test that it is enough.

kind regards


On 11/06/2024 18:20, Guo, Mr Yiming (Bill) Guo wrote:
> Dear Dr. Lorenzo Paulatto,
>
> Thank you for your reply.  I am working on three calculations,
>
> The calculations involve:
>
>  1. A Nitrogen-doped graphene layer (VC-relax/SCF)
>  2. Li2S6 (VC-relax/SCF).
>  3. The combined system to determine the lowest energy state and
>     calculate the binding energy of Li2S6 on the Nitrogen-doped
>     graphene layer.
>
>
> I have encountered an issue with the VC-relax cell_factor for the 
> Nitrogen-doped graphene layer. When I change the cell factor to 3, the 
> calculation proceeds without problems.
>
> Given my limited experience with Quantum ESPRESSO (only 1.5 months), 
> my approach has been to build the model first, perform structure 
> optimization, and finally conduct the SCF calculation.
>
> From my understanding, if the lattice parameters are unknown or need 
> optimization, I should use VC-relax. However, if the lattice 
> parameters are known and fixed, VC-relax is unnecessary.
>
> Could you please confirm if this approach is correct and advise on how 
> to properly set the cell factor for the Nitrogen-doped graphene layer? 
> Any additional insights or recommendations you can provide would be 
> greatly appreciated.
>
> Thank you for your time and assistance.
>
> I have attached the N-doepd graphene layer file as well.
> Li2S6 (2) 1.in 
> <https://liveuclac-my.sharepoint.com/:u:/g/personal/ucecuof_ucl_ac_uk/ESnKgHLpoR5Iqv16PqG-9FkBvDMGUWgaD-zgnp8YoBK3VA>
> NG 1.in 
> <https://liveuclac-my.sharepoint.com/:u:/g/personal/ucecuof_ucl_ac_uk/EZbXvMWIroZGkiYC_fayFpoBL4NU9_akxZoNgAQ4cmZW_A>
>
>
> Best regards,
> Bill Guo
> ------------------------------------------------------------------------
> *发件人:* users <users-bounces at lists.quantum-espresso.org> 代表 Lorenzo 
> Paulatto <lorenzo.paulatto at cnrs.fr>
> *发送时间:* 2024年6月11日 16:23
> *收件人:* users at lists.quantum-espresso.org 
> <users at lists.quantum-espresso.org>
> *主题:* Re: [QE-users] Pw.x Cell_factor issue
>
> ⚠ Caution: External sender
>
>
> Hello,
>
> you are doing a variable cell relaxation, but your input is not a 
> solid, hence the cell is collapsing.
>
> Do not use vc-relax for molecules (or whatever weird object you are 
> trying to simulate)
>
> hth
>
>
> On 11/06/2024 15:42, Guo, Mr Yiming (Bill) Guo wrote:
>> Dear Experts,
>>
>> I hope this message finds you well.
>>
>> I am currently performing a variable cell relaxation (vc-relax) 
>> calculation for Li2S6. However, I keep encountering the error 
>> message: "Not enough space allocated for radial FFT: try restarting 
>> with a larger cell_factor." According to the documentation, the 
>> recommended values for cell_factor during the pw.x execution are 2 or 
>> 1. Despite trying both values, the error persists. Interestingly, 
>> when I set cell_factor to 3, the calculation proceeds without any issues.
>>
>> Could you please advise if setting the cell_factor to 3 is 
>> appropriate for pw.x, or if there might be an underlying issue with 
>> my parameters?
>>
>> Thank you for your time and assistance.
>>
>> Best regards,
>> Bill Guo
>>
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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/ 
> <http://www.impmc.upmc.fr/~paulatto/> - https://anharmonic.github.io/ 
> <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 listusers at lists.quantum-espresso.org
> 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
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