[Pw_forum] flat band structure
Giovanni Cantele
giovanni.cantele at spin.cnr.it
Fri May 15 14:38:08 CEST 2015
It seems to me that the input files you provide DO NOT give rise to flat bands. I tried to run them, since the calculations last after few seconds, and the band structure is not flat.
Another question is whether your calculation corresponds to what reported in the paper you mention. Indeed, if you look carefully, the calculation reported therein concerns a three dimensional structure, that is rather obscure to me (see the Brillouin zone path, k-points coordinates change along k_x, k_y and k_y whereas you correctly choose a one-dimensional path).
The paper reports a unit cell a=6.52 A, b=c=1.304 A, which does not correspond to a linear chain, because 5-atom linear chains are parallel to x (6.52 ~ 1.306 * 5), but along y and z they are only 1.3 A far apart. So, try to understand if you want to reproduce the results of the paper, or calculate the band structure of a linear carbon chain, whose (not flat!) band structure is NOT that reported in Fig. 1 of the mentioned paper.
Giovanni
> On 15 May 2015, at 06:27, Zeina Al-Dolami <zaldolam at email.uark.edu> wrote:
>
> Dear users and developers,
> I posted the below question more than two weeks ago. However, I have not received any response. Any feedback or suggestion is greatly appreciated. Thanks in advance
>
> Zeina
> ---------- Forwarded message ----------
> From: Zeina Al-Dolami <zaldolam at email.uark.edu <mailto:zaldolam at email.uark.edu>>
> Date: Tue, Apr 28, 2015 at 3:54 PM
> Subject: flat band structure
> To: pw_forum at pwscf.org <mailto:pw_forum at pwscf.org>
>
>
> Dear Pwscf's developers and users,
> I have started using quantum espresso recently for my research that focuses on investigating the mechanical and electrical properties of carbon based materials. I ran several examples of wannier90-1.2 to gain more understanding and insight of what I need to consider when running simulations for quantum conductance. However, I have realized that I need to reproduce the band structures of carbon based materials that have been already published then move to using wannier90. I came across this paper http://scitation.aip.org/content/aip/proceeding/aipcp/10.1063/1.3469647 <http://scitation.aip.org/content/aip/proceeding/aipcp/10.1063/1.3469647> page242. It is basically a linear chain of 5 carbon atoms. Also, Accelrys Software, DMol programme, was used in this paper. I used the below scf and band files to reproduce the same band structure. However, the band structure that was produced contains flat bands only. I went through the pw-forum to find whether there was similar question or not. I found some discussions related to band structure and other suggestions that I have considered but no success, such as http://qe-forge.org/pipermail/pw_forum/2005-December/078012.html <http://qe-forge.org/pipermail/pw_forum/2005-December/078012.html> . Would you please tell me what I missed in my calculations? It is worth to mention that I have tried to use the same parameters available in this paper in my simulation. Any suggestion and feedback is greatly appreciated. Apologies if my question seems trivial because I am still at the beginning and have no background in this field. Looking forward to hearing from you. Thanks in advance
>
> Zeina
>
> scf file
>
> &CONTROL
> calculation = 'scf',
> restart_mode= 'from_scratch',
> verbosity = 'high'
> pseudo_dir = '/pseudo',
> outdir = './',
> prefix = '5cc',
> tstress = .f.,
> tprnfor = .t.,
> /
> &SYSTEM
> ibrav = 1,
> ! a = 6.520,
> ! b = 1.304,
> ! c = 1.304,
> celldm(1) = 12.3210,
> cosbc = 0.,
> cosac = 0.,
> cosab = 0.,
> nat = 5,
> ntyp = 1,
> ecutwfc = 30.,
> ecutrho = 240.,
> occupations = 'smearing',
> smearing = 'cold',
> degauss = 0.03,
> nspin = 1,
> /
> &ELECTRONS
> mixing_beta = 0.4
> electron_maxstep = 1000,
> conv_thr = 1.D-10,
> /
> ATOMIC_SPECIES
> C 12.0107 C.pbe-rrkjus.UPF
>
> ATOMIC_POSITIONS (angstrom)
> C 0.183 0.000000000 0.000000000
> C 1.489 0.000000000 0.000000000
> C 2.791 0.000000000 0.000000000
> C 4.093 0.000000000 0.000000000
> C 5.399 0.000000000 0.000000000
>
> K_POINTS {automatic}
> 6 1 1 0 0 0
>
>
>
> band file
> &CONTROL
> calculation = 'bands',
> restart_mode= 'from_scratch',
> verbosity = 'high'
> pseudo_dir = '/pseudo',
> outdir = './',
> prefix = '5cc',
> tstress = .f.,
> tprnfor = .t.,
> /
> &SYSTEM
> ibrav = 1,
> ! a = 6.520,
> ! b = 1.304,
> ! c = 1.304,
> celldm(1) = 12.3210,
> cosbc = 0.,
> cosac = 0.,
> cosab = 0.,
> nat = 5,
> ntyp = 1,
> ecutwfc = 30.,
> ecutrho = 240.,
> occupations = 'smearing',
> smearing = 'cold',
> degauss = 0.03,
> nspin = 1,
> /
> &ELECTRONS
> mixing_beta = 0.4
> electron_maxstep = 1000,
> conv_thr = 1.D-10,
> ! diag_full_acc = .true.
>
> /
> ATOMIC_SPECIES
> C 12.0107 C.pbe-rrkjus.UPF
>
> ATOMIC_POSITIONS (angstrom)
> C 0.183 0.000000000 0.000000000
> C 1.489 0.000000000 0.000000000
> C 2.791 0.000000000 0.000000000
> C 4.093 0.000000000 0.000000000
> C 5.399 0.000000000 0.000000000
>
> K_POINTS {crystal}
> 6
> 0.00000000 0.00000000 0.00000000 1.00000000
> 0.16666667 0.00000000 0.00000000 1.00000000
> 0.33333333 0.00000000 0.00000000 1.00000000
> 0.50000000 0.00000000 0.00000000 1.00000000
> 0.66666667 0.00000000 0.00000000 1.00000000
> 0.83333333 0.00000000 0.00000000 1.00000000
>
>
> --
> Zeina Al-Dolami
> PhD Candidate
> Microelectronics and Photonics Graduate Program
> University of Arkansas
> Fayetteville, AR 72701
> Office: PHYS 244
> Email: zaldolam at email.uark.edu <mailto:zaldolam at email.uark.edu> <mailto:cxm075 at email.uark.edu>
>
>
> --
> Zeina Al-Dolami
> PhD Candidate
> Microelectronics and Photonics Graduate Program
> University of Arkansas
> Fayetteville, AR 72701
> Office: PHYS 244
> Email: zaldolam at email.uark.edu <mailto:zaldolam at email.uark.edu> <mailto:cxm075 at email.uark.edu>_______________________________________________
> Pw_forum mailing list
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> http://pwscf.org/mailman/listinfo/pw_forum <http://pwscf.org/mailman/listinfo/pw_forum>
--
Giovanni Cantele, PhD
CNR-SPIN
c/o Dipartimento di Fisica
Universita' di Napoli "Federico II"
Complesso Universitario M. S. Angelo - Ed. 6
Via Cintia, I-80126, Napoli, Italy
e-mail: giovanni.cantele at spin.cnr.it
Phone: +39 081 676910
Skype contact: giocan74
ResearcherID: http://www.researcherid.com/rid/A-1951-2009
Web page: http://people.na.infn.it/~cantele
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