[Pw_forum] Change of occupation number and cut3d

[Duy Le]

2011/7/30 Samuel Poncé <samuel.pon at gmail.com>:
> I did try to add the variable tot_charge = +0.00046875 because I have 64 k
> points and 4 valences band ( 4-(63*4+3.97)/64)

Not sure what you were calculating. tot_charge is additional charge
you add to your system.
For example, if you have a system with 8 electron, and if you define
tot_charge = +1, you will have 8-1=7 electron in the system.

> However if I add the variable 'occupations = "fixed"' then I get the
> following WARNING:
>      WARNING: integrated charge=     8.00000000, expected=     7.99953125
>
> I off course get the exact same total energy as with tot_charge = 0 (this is
> not the expected behaviour).
>
> I did try without the variable 'occupation' (by the way what is the default
> value for occupation?) and also get the exact same total energy.

This does not depend on occupation. Read manual about occupation for
more details.
If you do a simple math: 7.99953125+0.00046875 you will see a "magic" number.


> I also do not understand why I don't have an occupation of 2.0 for all my
> valence states?
>
>  k = 0.0000 0.0000 0.0000 (  1243 PWs)   bands (ev):
>
>     -7.9264  13.7887  13.7887  13.7887
>
>      occupation numbers
>      0.0312   0.0312   0.0312   0.0312
you should post your input for further advice.
--------------------------------------------------
Duy Le
PhD Candidate
Department of Physics
University of Central Florida.

"Men don't need hand to do things"


>
>
> 2011/7/30 GAO Zhe <flux_ray12 at 163.com>
>>
>> Dear Ponce:
>> I am sorry that I may not catch the right meaning of your first question.
>> If you mean how to make extra or less charge for a model, you can use
>> "total_charge" in &system namelist.
>> If you wanna get information of wavefunction, you'd better read
>> Doc/INPUT_PP. For the charge density at specified k-point and band, you can
>> calculate |psi|^2 through pp.x. Moreover, if you want to obtain the charge
>> density for all k-points on specified bands, you can summary them by pp.x,
>> too. P.S.: the original code of pp.x can just allow 7 filepp, but you can
>> change the variable, nfilemax, in PP/chdens.f90, then make pp.x.
>> Good Luck.
>> --
>> GAO Zhe
>> CMC Lab, MSE, SNU, Seoul, S.Korea
>>
>> At 2011-07-29 17:27:27,"Samuel Poncé" <samuel.pon at gmail.com> wrote:
>>
>> Dear Quantum espresso user/developers,
>>
>> I have two questions:
>>
>> 1) Is it possible in pwscf to change "by hand" the occupation number ( and
>> impose a charge compensation accordingly) and if so how to do it?
>> I would like to do so because the sum over the different mode of the
>> partial derivative of the phonon frequency with respect of the occupation
>> number gives the zero point motion renormalization using Brooks theorem. I
>> would like to do this by finite difference (hence doing by hand some
>> calculation at different occupation number).
>>
>>  2) Is it possible to extract informations in text format form the
>> wavefunctions? What is the right post processing tool to do so? Like having
>> the value of the wavefunction for a defined k points and band index?
>>
>> Thanks you!
>>
>> Samuel Poncé.
>> (phD student, Université Catholique de Louvain, Belgium).
>>
>>
>>
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>
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