[QE-users] Symmetry dependent convergence

[Bidault, Xavier]

Hello Franklin,

IMO, the cutoff of 41 Ry is too short for a proper and stable structure convergence. How does the stress tensor compare at the last step of vc-relax, and at the verification step (latest stress tensor written in the output file)?

I'm more familiar with organic systems. But I think it doesn't require much more time to select conv_thr = 1e-6. Then, I find your mixing_beta really small. Default is 0.7, meaning 70% of the old guess is mixed with 30% of new, if I'm correct. But your value is 0.1, so you barely mix the old guess.

Finally, would there be known showstoppers for In, Cs and or Sb and the related PSlib PAW PP? I don't think so, but you can check it up on PSlib website.

Just my 2 cents.

Xavier Bidault

________________________________
From: users <users-bounces at lists.quantum-espresso.org> on behalf of Franklin T Cerasoli via users <users at lists.quantum-espresso.org>
Sent: Wednesday, April 6, 2022 5:52 PM
To: users at lists.quantum-espresso.org <users at lists.quantum-espresso.org>
Subject: [QE-users] Symmetry dependent convergence

Hello,

I've been using QE for several years and recently came across an interesting issue when try to converge certain large systems.

Attached is a link to an inputfile for a 216 atom system. With QE-6.8 (also tested on v6.3), the structure converges only if nosym=.f. and noinv=.f.. There are two symmetry operations found, the identity and inversion.

Setting nosym=.t. causes the estimated scf accuracy to thrash around in the hundreds of thousands of Ry, while nosym=.f. allows strong convergence (1e-6 Ry) within 30 iterations.

Pseudopotentials are all pslibrary PBE. Below is a link to the inputfile and relevant parts of the scf output.

I would appreciate any advice for understanding what the heck is going on here.

-Frank Cerasoli
UC Davis Department of Chemistry

From the outputs:

With nosym=.f.
     Program PWSCF v.6.8 starts on  4Apr2022 at 16:30:24
...
      2 Sym. Ops., with inversion, found
...
     iteration #  1     ecut=    41.00 Ry     beta= 0.10
...
     total energy              =  -84091.83957606 Ry
     estimated scf accuracy    <       7.57588335 Ry
...
     iteration #  2     ecut=    41.00 Ry     beta= 0.10
     total energy              =  -84090.73018546 Ry
     estimated scf accuracy    <       5.24675479 Ry

     iteration #  3     ecut=    41.00 Ry     beta= 0.10
...
     total energy              =  -84091.16546184 Ry
     estimated scf accuracy    <       0.84010802 Ry


With nosym=.t.
     Program PWSCF v.6.8 starts on  4Apr2022 at 18: 9:20
...
     No symmetry found
...
     iteration #  1     ecut=    41.00 Ry     beta= 0.10
...
     total energy              =  -83948.30076200 Ry
     estimated scf accuracy    <  364559.66452101 Ry

     iteration #  2     ecut=    41.00 Ry     beta= 0.10
...
     total energy              =  -84392.52517827 Ry
     estimated scf accuracy    <  209530.42525106 Ry

     iteration #  3     ecut=    41.00 Ry     beta= 0.10
...​
     total energy              =  -85690.00953396 Ry
     estimated scf accuracy    <  338759.15202062 Ry


And the inputfile is here:
https://drive.google.com/file/d/1jaF7drV996sg4ckxYunyHPpE79SRDdjZ/view?usp=sharing<https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdrive.google.com%2Ffile%2Fd%2F1jaF7drV996sg4ckxYunyHPpE79SRDdjZ%2Fview%3Fusp%3Dsharing&data=04%7C01%7Cxavbdlt%40uic.edu%7C3441e0b59e5b441888e608da1820480b%7Ce202cd477a564baa99e3e3b71a7c77dd%7C0%7C0%7C637848824348798187%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C2000&sdata=boGqNRGVk6%2FJ0GVhqmBt0e2dZh9yQwLom3%2FdG1KPPBU%3D&reserved=0>

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