# [Pw_forum] (no subject)

Paolo Giannozzi p.giannozzi at gmail.com
Tue Jul 4 12:33:24 CEST 2017

>From the header of next version of average.f90:

!      The planar average is defined as
!         p(k) = \sum_{i=1}^{N_1} \sum_{j=1}^{N_2} Q(i,j,k) / (N_1 N_2)
!      along direction 3, and the like for directions 1 and 2;
!      N_1, N_2, N_3 are the three dimensions of the 3D FFT.
!      Note that if Q is a charge density whose integral is Z_v:
!         Z_v = \int p(z) dV = \sum_k p(k) \Omega/N_3
!      where \Omega is the size of the unit cell (or supercell)

P.

On Tue, Jul 4, 2017 at 12:02 PM, VineetKumar Pandey <
vineetkumar.pandey at students.iiserpune.ac.in> wrote:

> dear sir, when we do average.x, we get charge per unit surface, I want to
> know unit of charge , I mean it's in electronic unit or coulomb. and sir I
> multiplied it by area. it's coming half of the charge in comparison with
> what it should be.
>
>
> thank you
>
> Vineet Kumar Pandey
> IISER PUNE, INDIA
> PINCODE-411008
>
> Phone: +91 8853094275 <+91%2088530%2094275>
>
>
> On Tue, Jul 4, 2017 at 2:49 PM, Thomas Brumme <
> thomas.brumme at uni-leipzig.de> wrote:
>
>> Dear Vineet Kumar,
>>
>> if you average the charge over a surface you'll get the charge per unit
>> surface. Integrating this will give you the total charge per unit surface...
>>
>> I think the output of average.x is just this... Thus, you'll need to
>> multiply by the xy-area of your unit cell...
>>
>> Regards
>>
>> Thomas
>>
>> On 07/04/17 11:08, VineetKumar Pandey wrote:
>>
>> I am trying to calculate charge density(rho)  as a function of z axis.
>> what I did by using pp.x and then average.x. but when I am integrating
>> rho(z)  with respect to z. I am not getting the total charge, that I have
>> in my system. can anybody help me to get out of it?  actually, my system is
>> PbI2. and it has 18 e- in a unit cell.
>> Vineet Kumar Pandey
>> IISER PUNE, INDIA
>> PINCODE-411008
>>
>> Phone: +91 8853094275 <+91%2088530%2094275>
>>
>>
>>
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>>
>> --
>> Dr. rer. nat. Thomas Brumme
>> Wilhelm-Ostwald-Institute for Physical and Theoretical Chemistry
>> Leipzig University
>> Phillipp-Rosenthal-Strasse 31
>> 04103 Leipzig
>>
>> Tel:  +49 (0)341 97 36456 <+49%20341%209736456>
>>
>> email: thomas.brumme at uni-leipzig.de
>>
>>
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>
>
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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
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