[Pw_forum] Pw_forum Digest, Vol 34, Issue 5

jia chen jiachen at princeton.edu
Fri Apr 2 22:44:47 CEST 2010 

Dear Prof Stefano de Gironcoli,

Thank you for your explanation. It is really helpful.
I have been using Quantum Espresso for a while. I like this project
very much and I hope I can do a little contribution to this community.
Since QE4.0, empty states feature in CP code didn't work anymore. I
added about ten lines to emptystartes.f90 module and it works in 4.1.1
and 4.1.2. I know people have other methods to do it, but this feather
may be handy, so I attached the code which may be useful, just in
case, for someone. I am not a good programmer, I can do nothing more
than making it work...

Best Regards
jia
On Fri, Apr 2, 2010 at 3:17 AM,  <pw_forum-request at pwscf.org> wrote:
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> Today's Topics:
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>   1. starting_magnetization and magnetization optimization in
>      pwscf (jia chen)
>   2. Re: starting_magnetization and magnetization optimization in
>      pwscf (Stefano de Gironcoli)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Thu, 1 Apr 2010 16:26:31 -0400
> From: jia chen <jiachen at princeton.edu>
> Subject: [Pw_forum] starting_magnetization and magnetization
>        optimization in pwscf
> To: pw_forum at pwscf.org
> Message-ID:
>        <y2sf033174e1004011326m6b76da56r56a8fe080e44ab2d at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
>
> Dear All,
>
> Pwscf has a very nice feature that can set initial magnetism of a
> certain kind of atom by starting_magnetization. It is working very
> well for me. But I would like to know more about how this is really
> working in cp code, during magnetization optimization calculations. It
> is too much for me to read the code to get the answer. So I would like
> to give a guess of basic idea of this process.
>
> When we start a calculation with initial atomic wave functions. Pwscf
> code can give atomic occupations of spin up and down whose ratio
> satisfy the value of starting_magnetization. During the calculation,
> pwscf can adjust the occupation number after each diagonal step
> according to orbitals energies because pwscf goes with a bunch of
> empty states. Then there can be "electron flow" between spin up and
> down. Basically, that's I guess how pwscf does magnetization
> optimization.
>
> Can you tell me what is the actual process pwscf goes though in this
> kind of magnetization optimizations? Any comments are very welcome.
> Thank you in advance.
>
> Best Wishes
> --
> Jia Chen
>
> Dept of Chemistry
> Princeton University
> Princeton, NJ 08544
>
>
> ------------------------------
>
> Message: 2
> Date: Thu, 01 Apr 2010 23:17:50 +0200
> From: Stefano de Gironcoli <degironc at sissa.it>
> Subject: Re: [Pw_forum] starting_magnetization and magnetization
>        optimization in pwscf
> To: PWSCF Forum <pw_forum at pwscf.org>
> Message-ID: <4BB50D7E.6000905 at sissa.it>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Dear Jia Chen,
>  the starting magnetization variable is used to define the initial
> charge density in a scf run in pwscf.
>  This density is used to build the first KS potential which thus
> results to have a magnetically broken symmetry.
>  The resulting spin-up and spin-down hamiltonians are diagonalized and
> the Fermi energy located from the constraint on the total number of
> electrons (the system must be treated as a metal and a number of empty
> states are present).
>  This determines the output density and since the potential is
> "magnetically ordered" the density also is if the system likes so.
>  Then the code mixes in and out densities and builds a new guess for
> the input density and hence the new KS potential and so on...
>   So starting magnetization really enters only in PW/atomic_rho.f90
> which  is used to build the starting guess for the  input charge density as
>
>   rho_up =  sum_s  (1.0+starting_magnetization_atom_s)/2 *
> unpolarized_rho_atom_s
>   rho_dw = sum_s  (1.0-starting_magnetization_atom_s)/2 *
> unpolarized_rho_atom_s
>
> Hope this helps,
>
> stefano
>
>
> jia chen wrote:
>> Dear All,
>>
>> Pwscf has a very nice feature that can set initial magnetism of a
>> certain kind of atom by starting_magnetization. It is working very
>> well for me. But I would like to know more about how this is really
>> working in cp code, during magnetization optimization calculations. It
>> is too much for me to read the code to get the answer. So I would like
>> to give a guess of basic idea of this process.
>>
>> When we start a calculation with initial atomic wave functions. Pwscf
>> code can give atomic occupations of spin up and down whose ratio
>> satisfy the value of starting_magnetization. During the calculation,
>> pwscf can adjust the occupation number after each diagonal step
>> according to orbitals energies because pwscf goes with a bunch of
>> empty states. Then there can be "electron flow" between spin up and
>> down. Basically, that's I guess how pwscf does magnetization
>> optimization.
>>
>> Can you tell me what is the actual process pwscf goes though in this
>> kind of magnetization optimizations? Any comments are very welcome.
>> Thank you in advance.
>>
>> Best Wishes
>>
>
>
>
> ------------------------------
>
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>
> End of Pw_forum Digest, Vol 34, Issue 5
> ***************************************
>



-- 
Jia Chen

Dept of Chemistry
Princeton University
Princeton, NJ 08544
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