[Pw_forum] Problem with PDOS of ionic crystals
Giovanni Cantele
giovanni.cantele at spin.cnr.it
Fri Apr 4 15:04:19 CEST 2014
it is not a matter of d orbitals, I mentioned them just as an example.
You are not able to calculate the full PDOS if the state you’re projecting possess (even partially) a character
(s, p, d, ….) which is not included in the pseudo potential.
The band structure / eigenvalues are instead correct (at DFT level of approximation), because they’re calculated
using plane waves as basis set, not atomic orbitals!
Giovanni
On 04 Apr 2014, at 13:30, Alexander G. Kvashnin <agkvashnin at gmail.com> wrote:
> Dear Giovanni,
>
> Thank you for your quick answer!
> As I understand correctly, I am not able to calculate correct PDOS while I have no d orbitals in the pseudo?
>
> --
> Sincerely yours,
> Alexander G. Kvashnin
> =====================================================
> PhD Student
> Moscow Institute of Physics and Technology http://mipt.ru/
> 141700, Institutsky lane 9, Dolgoprudny, Moscow Region, Russia
>
> Junior research scientist
> Technological Institute for Superhard
> and Novel Carbon Materials http://www.tisnum.ru/
> 142190, Central'naya St. 7a, Troitsk, Moscow Region, Russia
> =====================================================
>
>
> On 4 April 2014 13:18, Giovanni Cantele <giovanni.cantele at spin.cnr.it> wrote:
>
> On 04 Apr 2014, at 10:43, Alexander G. Kvashnin <agkvashnin at gmail.com> wrote:
>
>> Dear QE users,
>>
>> I tried to calculate PDOS for simple cubic NaCl structure. I performed an optimization vc-relax with 6x6x6 k-points, than I made scf calculations, nscf calculations and after that I ran projwfc to plot PDOS.
>> My question is why when I plotted DOS_Na+DOS_Cl it differs from the total DOS for whole system, specially in conduction band?
>>
>> Here is my nscf file and input file for projfwc:
>>
>> &control
>> calculation='nscf'
>> restart_mode='restart',
>> tstress = .true.
>> tprnfor = .true.
>> prefix='nacl',
>> pseudo_dir = '.',
>> outdir='.',
>> nstep = 200
>> /
>> &system
>> nosym = .false.,
>> ibrav = 1,
>> nat = 4,
>> ntyp = 2,
>> ecutwfc = 30,
>> celldm(1) = 10.750047341391399,
>> occupations = 'tetrahedra',
>> /
>> &electrons
>> conv_thr = 1.0d-8
>> mixing_beta = 0.7
>> electron_maxstep = 300
>> /
>> ATOMIC_SPECIES
>> Na 22.9897 Na.pbe-sp-van_ak.UPF
>> Cl 35.4527 Cl.pbe-n-van.UPF
>> ATOMIC_POSITIONS crystal
>> Na -0.500000000 -0.500000000 0.000000000
>> Na -0.500000000 0.000000000 -0.500000000
>> Cl -0.500000000 0.000000000 0.000000000
>> Cl -0.500000000 -0.500000000 -0.500000000
>> Cl 0.000000000 -0.500000000 0.000000000
>> Cl 0.000000000 0.000000000 -0.500000000
>> Na 0.000000000 0.000000000 0.000000000
>> Na 0.000000000 -0.500000000 -0.500000000
>> K_POINTS automatic
>> 6 6 6 0 0 0
>>
>> &inputpp
>> outdir='./'
>> prefix='nacl'
>> ngauss=1, degauss=0.02
>> DeltaE=0.05
>> Emin=-15.0, Emax=15.0,
>> filpdos='nacl.k'
>> /
>>
>>
>> Any suggestion are welcome!
>> Thank you in advance!
>> --
>> Sincerely yours,
>> Alexander G. Kvashnin
>> =====================================================
>> PhD Student
>> Moscow Institute of Physics and Technology http://mipt.ru/
>> 141700, Institutsky lane 9, Dolgoprudny, Moscow Region, Russia
>>
>> Junior research scientist
>> Technological Institute for Superhard
>> and Novel Carbon Materials http://www.tisnum.ru/
>> 142190, Central'naya St. 7a, Troitsk, Moscow Region, Russia
>> =====================================================
>>
>
>
>
> Dear Alexander,
>
> inside the pdos output file you should find, for EACH eigenvalue at EACH k-point the decomposition of
> the wave function, together with the sum of the square modulus of the expansion coefficients.
>
> What you should notice is that, while for occupied states |psi|^2 = 1.000, the coefficient square moduli do
> not sum up to 1, as you move to high energy unoccupied states.
>
> Should the basis set used for the projection be orthogonal and complete, that should not occur. However,
> the code, as far as I remember, is only able to project onto the atomic orbitals included in the pseudo potentials.
>
> Therefore, while the bands, even though unoccupied, are correctly (at DFT level!) computed, the projection onto
> the atomic orbitals might not be enough because would require atomic orbitals (e.g. d states) not included
> in the pseudo. The result is that the sum of the partial dos is LESS than the (correct) total DOS.
>
> Giovanni
>
> --
>
> 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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--
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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