[Pw_forum] MgO slab calculation: unexpected Fermi energy shift

[Yue-Wen Fang]

Dear Dingfu,

Thank you for your reply (LOL).

After making some tests, I find this error is not caused by the occupations
tag. The PBE pseudopotential cannot accurately reproduce the property of
the slab. I switched to pw91 as you said, and it works fine now. Thanks for
your discussion with me.

Bests
Fang

2016-04-23 9:19 GMT+09:00 Dingfu Shao <dingfu.shao at gmail.com>:

> Hi, Yue-Wen,
>
> You need to set occupations='fixed'  for insulator. 'Smearing' is for
> metal.
>
> Best regards,
>
> Ding-Fu
>
>
>
>
> *Ding-Fu Shao, Ph. D.*
>
>
> *Department of Physics and Astronomy, University of Nebraska-Lincoln*
>
> *Lincoln, NE **68588-0299*
>
> *Email: dingfu.shao at gmail.com <dingfu.shao at gmail.com>*
>
> 2016-04-22 4:43 GMT-05:00 Yue-Wen Fang <yuewen.fang at gmail.com>:
>
>> Dear all,
>>
>> I calculated a MgO slab model with two* symmetrical* interface using 3
>> different DFT codes using plane wave method. The other two shows this slab
>> is an insulator, and the results are almost completely same.
>>
>> However, pwscf calculation show it is a metal with an unexpected Fermi
>> shift in the density of states although the shape of DOS is similar to
>> those obtained from other DFTcodes. I think this is caused my incorrect
>> settings, but I haven't found what specific factor causes this error.
>>
>> The scf and nscf input files are shown in the last part, hopefully
>> experts could give some suggestions. Many thanks.
>>
>> *PS:*
>> Because it is just a test, I only used about 6 Angstrom in this model. I
>> checked the potential in every DFT code, there is no slope of potential in
>> vacuum, which indicates there is no unexpected artificial field is induced.
>>
>>
>> *SCF calculation input:*
>>
>> &control
>>  calculation = 'scf',
>>  verbosity = 'high',
>>  restart_mode = 'from_scratch',
>>  prefix = 'mgo',
>>  tstress = .false.,
>>  tprnfor = .false.,
>>  pseudo_dir = '.',
>>  outdir = '.'
>>  wf_collect=.true.
>> /
>> &system
>>  ibrav=0, nat=6, ntyp=2,
>>  ecutwfc=25,
>>  ecutrho=300,
>>  occupations='smearing',
>>  smearing='gaussian',
>>  degauss=0.001,
>> /
>> &electrons
>>  diagonalization='david',
>>  mixing_mode = 'plain',
>>  mixing_beta = 0.7,
>>  conv_thr =  1.0d-7,
>> /
>> ATOMIC_SPECIES
>>  Mg 24.305000 Mg.pbe-nsp-bpaw.UPF
>>  O 15.999400 O.pbe-van_ak.UPF
>> ATOMIC_POSITIONS crystal
>>  Mg 0.000000 0.000000 0.370955
>>  Mg 0.500000 0.500000 0.500000
>>  Mg 0.000000 0.000000 0.629045
>>  O 0.500000 0.500000 0.370955
>>  O 0.000000 0.000000 0.500000
>>  O 0.500000 0.500000 0.629045
>> K_POINTS {Automatic}
>> 7 7 1 0 0 0
>> CELL_PARAMETERS bohr
>> 5.627166 0.000000 0.000000
>> 0.000000 5.627166 0.000000
>> 0.000000 0.000000 30.834283
>>
>>
>> *NSCF calculation input:*
>>
>> &control
>>  calculation = 'nscf',
>>  verbosity = 'high',
>>  restart_mode = 'from_scratch',
>>  prefix = 'mgo',
>>  tstress = .false.,
>>  tprnfor = .false.,
>>  pseudo_dir = '.',
>>  outdir = '.'
>>  wf_collect=.true.
>> /
>> &system
>>  ibrav=0, nat=6, ntyp=2,
>>  ecutwfc=25,
>>  ecutrho=300,
>>  occupations='tetrahedra',
>> /
>> &electrons
>>  diagonalization='david',
>>  mixing_mode = 'plain',
>>  mixing_beta = 0.7,
>>  conv_thr =  1.0d-7,
>> /
>> ATOMIC_SPECIES
>>  Mg 24.305000 Mg.pbe-nsp-bpaw.UPF
>>  O 15.999400 O.pbe-van_ak.UPF
>> ATOMIC_POSITIONS crystal
>>  Mg 0.000000 0.000000 0.370955
>>  Mg 0.500000 0.500000 0.500000
>>  Mg 0.000000 0.000000 0.629045
>>  O 0.500000 0.500000 0.370955
>>  O 0.000000 0.000000 0.500000
>>  O 0.500000 0.500000 0.629045
>> K_POINTS {Automatic}
>> 11 11 2 0 0 0
>> CELL_PARAMETERS bohr
>> 5.627166 0.000000 0.000000
>> 0.000000 5.627166 0.000000
>> 0.000000 0.000000 30.834283
>>
>> --
>>
>> ------------------------------------------------------------------------------------------------------------
>> Yue-Wen FANG, PhD student
>> East China Normal University <http://english.ecnu.edu.cn/>, China
>> Japan Fine Ceramics Center, Japan
>>
>>
>>
>>
>> _______________________________________________
>> Pw_forum mailing list
>> Pw_forum at pwscf.org
>> http://pwscf.org/mailman/listinfo/pw_forum
>>
>
>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://pwscf.org/mailman/listinfo/pw_forum
>



-- 
------------------------------------------------------------------------------------------------------------
Yue-Wen FANG, PhD student
East China Normal University <http://english.ecnu.edu.cn/>, China
Japan Fine Ceramics Center, Japan
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20160423/a7a23a68/attachment.html>