[Pw_forum] energy of 33CNT

Nicholas E. Singh-Miller nedward at MIT.EDU
Thu Jan 10 07:28:34 CET 2008

```Hi Zhu,

The Fermi energy (and the Kohn-Sham eigenvalues for that matter) found in
the output file are referenced specifially to the potential for the
calculation.  So to recover the 4~5 eV that you are expecting you need to
determine the vacuum potential.

hope that helps,

Nicholas

On Thu, 10 Jan 2008, Zhu Xi wrote:

> Hi Nicholas,
> thanks for your reply, but to my understaning, the 0.625eV fermi energy is
> wrong, it should be between -5~-4eV, I don't know why the code give such a
> fermi energy.....
>
>
> On 1/10/08, Nicholas E. Singh-Miller <nedward at mit.edu> wrote:
>>
>> Dear Zhu Xi,
>>
>> I have not run your input file, but assuming that it is correct and this
>> 0.625eV is what you read directly from the output, this Fermi energy
>> should also be correct.  If you are interested in the work function of
>> the (3,3)CNT you will have to obtain the difference between a vacuum
>> potential and the Fermi energy.  In short the potential in the vacuum != 0
>> due to the use of periodic boundary conditions.  If you  use pp.x to
>> obtain the potential remember that is is output in Rydbergs.   This is all
>> discussed other times on the forum.
>>
>> best of luck,
>>
>> Nicholas
>>
>> On Thu, 10 Jan 2008, Zhu Xi wrote:
>>
>>> Dear users,
>>>
>>> I run a scf calculation of (3,3)CNT, but the fermi energy is 0.652eV,
>> can
>>> anyone give some suggestion? thanks
>>>
>>>
>> ====================================================================================
>>>
>>> &control
>>>         calculation='scf',
>>>         PSEUDO_DIR='./',
>>>         prefix='33',
>>>         forc_conv_thr=1.0D-4,
>>> /
>>> &SYSTEM
>>>         ibrav = 0,
>>>          celldm(1)= 18.8972612499,
>>>        nat = 12,
>>>         ntyp = 1,
>>>         ecutwfc = 40.0 ,
>>>         nosym = .true. ,
>>>         nbnd  = 48 ,
>>>   occupations= 'smearing',degauss = 0.001
>>>
>>> /
>>> &electrons
>>>        conv_thr    = 1.D-6,
>>>        mixing_beta = 0.5D0,
>>> /
>>> CELL_PARAMETERS
>>>     1.0    0.000000000    0.000000000
>>>     0.000000000    1.0    0.000000000
>>>     0.000000000    0.000000000     0.245951
>>> ATOMIC_SPECIES
>>>    C    12.00000  C.pz-vbc.UPF
>>> ATOMIC_POSITIONS (crystal)
>>> C        0.625289967   0.669611155   0.250000000
>>> C        0.487077242   0.709466388   0.250000000
>>> C        0.291384631    0.523168925   0.250000000
>>> C        0.374710033   0.330388845   0.750000000
>>> C        0.512922758   0.290533612   0.750000000
>>> C        0.708615369   0.476831075   0.750000000
>>> C        0.416429985   0.692001578    0.750000000
>>> C        0.675464001   0.616817067   0.750000000
>>> C        0.312292454   0.592869751   0.750000000
>>> C        0.583570015   0.307998422   0.250000000
>>> C        0.324535999   0.383182933   0.250000000
>>> C        0.687707546   0.407130249   0.250000000
>>> K_POINTS automatic
>>> 1 1 11 0 0 0
>>>
>>> ==================================================
>>>
>>
>> *****************************************
>> Nicholas E. Singh-Miller
>> Ph.D. Candidate
>> Prof. Marzari Group (quasiamore.mit.edu)
>> Materials Science and Engineering
>> Massachusetts Institute of Technology
>> 13-4066
>> (617)324-0372
>> *****************************************
>> _______________________________________________
>> Pw_forum mailing list
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>>
>
>
>
>

*****************************************
Nicholas E. Singh-Miller
Ph.D. Candidate
Prof. Marzari Group (quasiamore.mit.edu)
Materials Science and Engineering
Massachusetts Institute of Technology
13-4066
(617)324-0372
*****************************************

```