[QE-users] nscf in super cell

[Fariba Islam]

Dear all,
My  conv_thr=1e-20 and ecutwfc=200 ecutrho=800
My nscf calculation is crashing with the error

task #        10
     from c_bands : error #         1
     too many bands are not converged

How can I solve ?

On Tuesday, May 12, 2020, Fariba Islam <ezqhaz at gmail.com> wrote:

> Thanks
>
> On Tue, May 12, 2020 at 12:41 PM Paolo Giannozzi <p.giannozzi at gmail.com>
> wrote:
>
>> On Tue, May 12, 2020 at 7:08 AM Fariba Islam <ezqhaz at gmail.com> wrote:
>>
>>> I wrote the following code for nscf calculation of a silicon supercell.
>>> Why do I get
>>>
>> "c_bands:  2 eigenvalues not converged
>>>  c_bands:  1 eigenvalues not converged...." in my output file and the
>>> calculation is not stopping
>>>
>>
>> if it is not stopping, there is no problem. In a scf calculation, the
>> iterative diagonalization starts from wavefunctions computed at the
>> previous scf step and usually converges quickly. The maximum number of
>> internal iterations is thus small (20 if I remember correctly). In a
>> non-scf calculation, there isn't such a good starting point and iterative
>> diagonalization sometimes does not converge for all eigenvalues in 20
>> iterations, but it is usually sufficient to repeat the diagonalization.
>>
>> Paolo
>>
>> &control
>>>     calculation = 'nscf'
>>>     restart_mode='from_scratch'
>>>     prefix = 'si_b'
>>>     outdir='./tmp/'
>>>     pseudo_dir='../pseudo/'
>>> /
>>> &system
>>>     ibrav=2, celldm(1) = 20.8218,
>>>     nat=16, ntyp=1,
>>>     ecutwfc=40
>>>     ecutrho=160
>>>     noinv=.true.
>>>     nosym=.true.
>>>     occupations='smearing' , smearing='gaussian',degauss=0.005
>>> /
>>> &electrons
>>>     conv_thr=1e-8
>>> /
>>> ATOMIC_SPECIES
>>>  Si  28.0855  Si_ONCV_PBE-1.0.upf
>>>
>>> ATOMIC_POSITIONS (alat)
>>> Si 0.000000   0.000000   0.000000
>>> Si -0.374989   0.375011   0.375011
>>> Si -0.250000   0.250000   0.000000
>>> Si -0.624989   0.625011   0.375011
>>> Si 0.000000   0.250000   0.250000
>>> Si -0.374989   0.625011   0.625011
>>> Si -0.250000   0.500000   0.250000
>>> Si -0.624989   0.875011   0.625011
>>> Si -0.250000   0.000000   0.250000
>>> Si -0.624989   0.375011   0.625011
>>> Si -0.500000   0.250000   0.250000
>>> Si -0.874989   0.625011   0.625011
>>> Si -0.250000   0.250000   0.500000
>>> Si -0.624989   0.625011   0.875011
>>> Si -0.500000   0.500000   0.500000
>>> Si -0.874989   0.875011   0.875011
>>>
>>> K_POINTS {automatic}
>>> 12 12 12 0 0 0
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>>
>>
>>
>> --
>> Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
>> Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
>> Phone +39-0432-558216, fax +39-0432-558222
>>
>> _______________________________________________
>> Quantum ESPRESSO is supported by MaX (www.max-centre.eu/quantum-espresso)
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>> https://lists.quantum-espresso.org/mailman/listinfo/users
>
>
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