[QE-users] Issue with Nanoribbon Band Structure of GeI

[Larry Shi]

Dear Mr. Karpati,

Thanks for your reply. I increased nbnd but the results are still the same;
the bands are still completely straight (attached below). There is supposed
to be a single Dirac point at Γ.

It looks like there is something fundamentally wrong with the input. Do you
have any idea what could be the cause of the problem? Are there any special
variables I need to use for nanoribbons?

Thank you for your help.

Larry

[image: image.png]

On Wed, Aug 5, 2020 at 7:24 AM Tamas Karpati <tkarpati at gmail.com> wrote:

> Dear Larry,
>
> You have almost 300 electrons which means ca. 150 occupied bands,
> while you forced QE to use just 2^7. Funny that SCF converged, proves
> stability of PWscf :)
>
> Try to increase nbnd above 150.
>
> Hope this helps,
>   t
>
>
> On Wed, Aug 5, 2020 at 3:55 AM Larry Shi <larryshi02 at gmail.com> wrote:
>
>> Dear QE gurus,
>>
>> I am new to QE and I am currently trying to replicate the band structure
>> for a GeI nanoribbon (https://doi.org/10.1103/PhysRevB.89.115429). I
>> passivated the Ge atoms with H atoms. When I run the band input file
>> (below) after the SCF has been converged, the bands in the resulting band
>> structure are all straight lines (they all have constant energy), which is
>> absurd. I'm not sure where the issue originates.
>>
>> Any assistance would be greatly appreciated!
>>
>>
>> &CONTROL
>>     calculation = "bands"
>>     max_seconds =  5.18400e+06
>>     pseudo_dir  = "C:\Users\User\.burai\.pseudopot"
>> /
>>
>> &SYSTEM
>>     a                         =  4.62000e+01
>>     angle1(1)                 =  0.00000e+00
>>     angle1(2)                 =  0.00000e+00
>>     angle2(1)                 =  0.00000e+00
>>     angle2(2)                 =  0.00000e+00
>>     b                         =  7.01480e+00
>>     c                         =  3.00000e+01
>>     cosab                     = -5.00000e-01
>>     degauss                   =  1.00000e-02
>>     ecutrho                   =  1.00000e+02
>>     ecutwfc                   =  2.50000e+01
>>     ibrav                     = 8
>>     lspinorb                  = .FALSE.
>>     nat                       = 32
>>     nbnd                      = 128
>>     nspin                     = 1
>>     ntyp                      = 3
>>     occupations               = "smearing"
>>     smearing                  = "gaussian"
>>     starting_magnetization(1) =  0.00000e+00
>>     starting_magnetization(2) =  0.00000e+00
>> /
>>
>> &ELECTRONS
>>     conv_thr         =  1.00000e-07
>>     electron_maxstep = 200
>>     mixing_beta      =  7.00000e-01
>>     startingpot      = "atomic"
>>     startingwfc      = "atomic+random"
>> /
>>
>> &BANDS
>>     lsym           = .FALSE.
>>     spin_component = 1
>> /
>>
>> K_POINTS {tpiba_b}
>> 3
>> Z      40
>> gG     40
>> Z      40
>>
>> ATOMIC_SPECIES
>> Ge     72.61000  Ge.pbe-n-rrkjus_psl.1.0.0.UPF
>> I     126.90447  I.pbe-mt_bw.UPF
>> H       1.00794  H.pbe-rrkjus.UPF
>>
>> ATOMIC_POSITIONS {angstrom}
>> H      -2.005606   1.098069  29.911525
>> Ge      0.019394   2.178887   0.673171
>> Ge      1.988303   1.098069  29.911525
>> I       0.170697   2.062988   3.223532
>> I       2.089141   1.028047  27.356392
>> H      -2.005606   5.686290   0.673171
>> Ge     -0.036697   4.605472  29.911525
>> I       0.064141   4.535450  27.356392
>> Ge      4.069394   2.178887   0.673171
>> Ge      6.038303   1.098069  29.911525
>> I       4.220697   2.062988   3.223532
>> I       6.139141   1.028047  27.356392
>> Ge      2.044394   5.686290   0.673171
>> Ge      4.013303   4.605472  29.911525
>> I       2.195697   5.570391   3.223532
>> I       4.114141   4.535450  27.356392
>> Ge      8.119394   2.178887   0.673171
>> Ge     10.088303   1.098069  29.911525
>> I       8.270697   2.062988   3.223532
>> I      10.189141   1.028047  27.356392
>> Ge      6.094394   5.686290   0.673171
>> Ge      8.063303   4.605472  29.911525
>> I       6.245697   5.570391   3.223532
>> I       8.164141   4.535450  27.356392
>> Ge     12.169394   2.178887   0.673171
>> H      14.138303   1.098069  29.911525
>> I      12.320697   2.062988   3.223532
>> Ge     10.144394   5.686290   0.673171
>> Ge     12.113303   4.605472  29.911525
>> I      10.295697   5.570391   3.223532
>> I      12.214141   4.535450  27.356392
>> H      14.138303   5.686290   0.673171
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