[Pw_forum] Problem with PDOS of ionic crystals

[Giovanni Cantele]

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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