Re: [Phonopy-users] BRMIX: very serious problems the old and the new charge density differ
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Re: [Phonopy-users] BRMIX: very serious problems the old and the new charge density differ
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From: FonsPaul <pau...@ai...> - 2019-10-23 00:20:08
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Hi Robert,
I was borrowing wisdom from the atomate python library. The queuing system automatically recovers from certain types of errors and I was paraphrasing the source code in my reply to you. If the job is not finishing, then recycling the WAVECAR file will not work. I would move on to Kerker mixing (IMIX=1) and see if that helps. You should read the details of the mixing process to understand the flags. I have also found that using ALGO=all (all bands simultaneous update of orbitals) avoids the mixing problems on occasion. There is a minimal amount of information on the forums, but there is no idea solution that works in all BRIX failure cases I think it is fair to say.
Best wishes,
Paul
Dr. Paul Fons
Chief Researcher
Systematic Materials Design Group
Nanoelectronics Research Institute
National Institute for Advanced Industrial Science & Technology, METI
AIST Central 5, Higashi 1-1-1Tsukuba, Ibaraki JAPAN 305-8565
tel. +81-298-61-5636fax. +81-298-61-2939
email: pau...@ai...<mailto:pau...@ai...>
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From: "Appleton, Robert J" <ra...@ca...>
Reply-To: "pho...@li..." <pho...@li...>
Date: Wednesday, October 23, 2019 5:37
To: "pho...@li..." <pho...@li...>
Subject: Re: [Phonopy-users] BRMIX: very serious problems the old and the new charge density differ
Hi P. Fons,
Quick question. In the first suggest, you say to “rerun” with ISTART=1 and the CHGCAR file from previous run. So to use ISTART=1 I need a WAVECAR from a previous run. When I get the BRMIX error the calculation doesn’t seem to end. So my question is how can I rerun with ISTART=1 without the first run every completing? Or are you suggesting to use the WAVECAR and CHGCAR from the optimization step? I am confused by what you mean by previous run if any attempt at this job has resulted in an error that prevents it from finishing. If you can help me clear this up I would appreciate it .
Thanks,
Robert
From: FonsPaul <pau...@ai...>
Sent: Tuesday, October 22, 2019 6:09 AM
To: pho...@li...
Subject: Re: [Phonopy-users] BRMIX: very serious problems the old and the new charge density differ
In regards to the BRMIX problem, there are several solutions to try. The follow suggestions are based upon the fallback code in Custodian, the Python based automated queuing system for VASP. From looking at the source code for Custodian, they suggest
1. Rerun the job using ISTART=1 and the CHGCAR file from the previous run
or if that doesn’t work
2. Use Kerker mixing (IMIX=1) — read the section on charge density mixing in the VASP manual for more information
3. Increase the KPOINT density.
I should add that another alternative I have tried successfully in the past is to use the ALGO=all for the diagonalization algorithm. It is more memory intensity and you may or may not have problems with memory depending on the size of the cell and the amount of memory you have in your machine.
P. Fons
National Institute of Advanced Industrial Science and Technology
Chief Senior Researcher
Sent from my iPad
________________________________
From: Alexander Pisch <ale...@si...<mailto:ale...@si...>>
Sent: Tuesday, October 22, 2019 1:27:39 PM
To: pho...@li...<mailto:pho...@li...> <pho...@li...<mailto:pho...@li...>>
Subject: Re: [Phonopy-users] BRMIX: very serious problems the old and the new charge density differ
Hi Robert,
what do you mean when you say that the phonon dispersions were not good ? If you observe negative frequencies, this would just mean that your structure is dynamically unstable, which happens sometimes when your structure is not the ground state.
Could you please send the full information for the VASP calculation ? (INCAR and KPOINTS for the relax step, which POTCAR you use and the full POSCAR file). I will try to reproduce your error.
cheers,
Alex
________________________________
De: "Appleton, Robert J" <ra...@ca...<mailto:ra...@ca...>>
À: pho...@li...<mailto:pho...@li...>
Envoyé: Lundi 21 Octobre 2019 20:28:51
Objet: [Phonopy-users] BRMIX: very serious problems the old and the new charge density differ
I understand the error I am referring to is a vasp issue and not specifically a phonopy issue, however, I have registered for the vasp forum and have been waiting for weeks to get an activation email. I am hoping that maybe posting my problem here I might find some help. If you have insight please feel free to reply.
I am calculating force sets on finite displacements generated by phonopy. My structure is TlNbO3 and phonopy generates 3 displacement poscars. When I used a 2x2x2 supercell and calculated the force sets there were no issues or errors. However, the phonon dispersions were no good and so I increased the size of the supercell to 3x3x3. When I went to calculate the force sets in vasp 2 of the 3 calculations gave me an error while 1 ran just fine.
The error reads: " BRMIX: very serious problems the old and the new charge density differ". The error appears about 10 DAV steps in for one run and about 5 DAV steps in for the other.
The incar I used for the 2x2x2 and what I started with for the 3x3x3 has the following:
PREC = Accurate
ENCUT = 600.0
EDIFF = 1e-8
IBRION = -1
NELMIN = 6
ISMEAR = 0
SIGMA = 0.01
LREAL = FALSE
LWAVE = FALSE
LCHARG = FALSE
Again, this worked just fine for 2x2x2 and for 1 of the displacements for the 3x3x3 supercell. To try and solve the error I searched online and was suggested to include ADDGRID = TRUE and ISYM = 0 in the incar. I tried this and still received the error. I optimized the structe with a 12x12x12 kmesh and am using a 4x4x4 kmesh for the calculation of the force sets on the finite displacements with a 3x3x3 supercell. Any suggestions on how to fix this issue would be appreciated. I can include more information if needed. Thanks.
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