[Pw_forum] Pw_forum Digest, Vol 34, Issue 5

Stefano Baroni baroni at sissa.it
Sat Apr 3 21:13:31 CEST 2010 

thank you - we really appreciate
SB

On Apr 2, 2010, at 10:44 PM, jia chen wrote:

> 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:
>> 
>>   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
>>> 
>> 
>> 
>> 
>> ------------------------------
>> 
>> _______________________________________________
>> Pw_forum mailing list
>> Pw_forum at pwscf.org
>> http://www.democritos.it/mailman/listinfo/pw_forum
>> 
>> 
>> End of Pw_forum Digest, Vol 34, Issue 5
>> ***************************************
>> 
> 
> 
> 
> -- 
> Jia Chen
> 
> Dept of Chemistry
> Princeton University
> Princeton, NJ 08544
> <emptystates.f90>_______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
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---
Stefano Baroni - SISSA  &  DEMOCRITOS National Simulation Center - Trieste
http://stefano.baroni.me [+39] 040 3787 406 (tel) -528 (fax) / stefanobaroni (skype)

La morale est une logique de l'action comme la logique est une morale de la pensée - Jean Piaget

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