[Pw_forum] Total forces of relaxing metallic system decreases then increases gradually

[Stefano de Gironcoli]

is the energy decreasing ? if so the relaxation is not yet finished.

stefano


On 18/02/2018 02:55, Hind Almisbahi wrote:
>
> Dear experts of quantum espresso,
>
> I am doing relaxation and the problem is that the total force is 
> decreasing until the 4^th scf, then start to increase gradually. The 
> system does not converge. Actually, I need to calculate the band 
> structure and see the band gap of Armchair graphene ribbon. The ribbon 
> width is composed of 17 carbon atoms (N=3p+2 family), so it is 
> metallic. I have one unit cell of the ribbon. I read in this mailing 
> list many useful discussions about suitable input for metallic systems 
> and I followed them as I understand. The version of quantum espresso 
> is 6.1.
>
> I tried many options of the input script but all the runs have the 
> same problem, total force is decreasing until the 4^th scf then start 
> to increase gradually. This is a complete version of my input:
>
> &CONTROL
>
> calculation='relax',
>
> outdir='.\Work',
>
> prefix='Arm17',
>
> pseudo_dir='C:\qe-6.1\pseudo',
>
> verbosity='high',
>
> etot_conv_thr= 1.0D-3,
>
> forc_conv_thr=1.0d-2,
>
> /
>
> &SYSTEM
>
> ibrav=8,
>
> a=41.1089d0,
>
> b=4.26258d0,
>
> c=20.0d0,
>
> nat=34,
>
> ntyp=1,
>
> ecutwfc=65,
>
> ecutrho=520,
>
> nbnd=76
>
> occupations='smearing',
>
> smearing='marzari-vanderbilt',
>
> degauss=0.001d0,
>
> /
>
> &ELECTRONS
>
> conv_thr=1d-06,
>
> mixing_beta=0.7d0,
>
> mixing_mode='local-TF'
>
> mixing_ndim=12
>
> diagonalization='cg'
>
> /
>
> &IONS
>
> /
>
> ATOMIC_SPECIES
>
> C 12.010700d0 C.pbe-rrkjus.UPF
>
> ATOMIC_POSITIONS {crystal}
>
> C0.0336555229d00.6666666956d00.5000000000d0
>
> C0.0919486003d00.8333333913d00.5000000000d0
>
> C0.0336555229d00.3333333044d00.5000000000d0
>
> C0.1502416777d00.6666666956d00.5000000000d0
>
> C0.2085347551d00.8333333913d00.5000000000d0
>
> C0.0919486003d00.1666666087d00.5000000000d0
>
> C0.1502416777d00.3333333044d00.5000000000d0
>
> C0.2668277852d00.6666666956d00.5000000000d0
>
> C0.3251206731d00.8333333913d00.5000000000d0
>
> C0.2085347551d00.1666666087d00.5000000000d0
>
> C0.2668277852d00.3333333044d00.5000000000d0
>
> C0.3834141768d00.6666666956d00.5000000000d0
>
> C0.4417072068d00.8333333913d00.5000000000d0
>
> C0.3251206731d00.1666666087d00.5000000000d0
>
> C0.3834141768d00.3333333044d00.5000000000d0
>
> C0.5000002369d00.6666666956d00.5000000000d0
>
> C0.5582932669d00.8333333913d00.5000000000d0
>
> C0.4417072068d00.1666666087d00.5000000000d0
>
> C0.5000002369d00.3333333044d00.5000000000d0
>
> C0.6165862969d00.6666666956d00.5000000000d0
>
> C0.6748793269d00.8333333913d00.5000000000d0
>
> C0.5582932669d00.1666666087d00.5000000000d0
>
> C0.6165862969d00.3333333044d00.5000000000d0
>
> C0.7331723570d00.6666666956d00.5000000000d0
>
> C0.7914653870d00.8333333913d00.5000000000d0
>
> C0.6748793269d00.1666666087d00.5000000000d0
>
> C0.7331723570d00.3333333044d00.5000000000d0
>
> C0.8497584170d00.6666666956d00.5000000000d0
>
> C0.9080514470d00.8333333913d00.5000000000d0
>
> C0.7914653870d00.1666666087d00.5000000000d0
>
> C0.8497584170d00.3333333044d00.5000000000d0
>
> C0.9663444771d00.6666666956d00.5000000000d0
>
> C0.9080514470d00.1666666087d00.5000000000d0
>
> C0.9663444771d00.3333333044d00.5000000000d0
>
> K_POINTS {automatic}
>
> 150 1 0 0 0
>
> These are some of the many options that I have explored:
>
> The above potential is ultrasoft, I used also norm conserving 
> (C.pbe-mt_gipaw.UPF).
>
> Smearing: I used methfessel-paxton and marzari-vanderbilt
>
> Degause: I used 0.01 and 0.001
>
> mixing_beta: I used 0.1 and 0.7
>
> mixing_mode: I used local-TF and TF
>
> mixing_ndim: I used 8 and 12
>
> diagonalization: I used cg and david
>
> ecutwfc: I used 65 and 75
>
> ecutrho: with norm conserving (ecutwfc*4 and ecutwfc*10), with 
> ultrasoft (ecutwfc*8)
>
> nbnd=76 (I have 34 atoms, so 136 valence electrons which need 68 
> bands, because it is metallic I added 8 extra bands)
>
>
> Previously I have successfully calculated the band structure and band 
> gap of semiconductor ribbon but I could not do the calculation of 
> metallic ribbon. I appreciate any help to solve my problem, why the 
> forces always increase after the 4^th scf?
>
>
> ​
>
> Best Regards,
>
> Hind
>
> Lecturer, IT department
>
> King Abdulaziz University
>
>
>
> Disclaimer: The information contained in this message is intended for 
> the addressee only and may contain classified information. If you are 
> not the addressee, please delete this message and notify the sender; 
> you should not copy or distribute this message or disclose its 
> contents to anyone. Any views or opinions expressed in this message 
> are those of the individual(s) and not necessarily of the university. 
> No reliance may be placed on this message without written confirmation 
> from an authorized representative of its contents. No guarantee is 
> implied that this message or any attachment is virus free or has not 
> been intercepted and amended.
>
> إخلاء مسؤليه:  ان جميع المعلومات المتضمنة في هذه الرسالة تخص المستلم، 
> وربما تتضمن معلومات سرية، واذا لم تكن انت المستلم فالرجاء الغاء 
> الرسالة واشعار المرسل، كما يمنع نسخ او توزيع هذه الرسالة او افشاء 
> محتوياتها لاخرين. ويجدر بالعلم ان جميع الآراء ووجهات النظر الواردة في 
> هذه الرسالة تعتبر شخصية وليست بالضرورة منسوبة للجامعة. كما لايمكن ان 
> يعتمد على هذه الرسالة ما لم تحصل على موافقة خطية من المسئول عن 
> محتوياتها. كما لايوجد ضمان بان هذه الرسالة أو مرفقاتها خالية من 
> الفيروسات أو انها لم يتم اعتراضها وتعديلها
>
>
>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://pwscf.org/mailman/listinfo/pw_forum

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20180218/677501df/attachment.html>