The ABINIT Users Mailing List ( CLOSED )

[Pawel Scharoch <Pawel.Scharoch@pwr.wroc.pl>]

   Dear colleagues,

     there is one think I do not  quite understand. I would think that 
 kinetic energy is the density functional and assumes a particular 
 value for the ground state density. The ground state density, once 
 it has been calculated in the SC procedure, with the use of special k-points,
 does not depend on a particular choice of k-points any more, neither 
 the kinetic energy does! What is the problem then ?

   With best regards,

    Pawel

----- Oryginalna wiadomość -----
Od: "Allan, Douglas C Dr" <AllanDC@corning.com>
Data: Sroda, Czerwiec 13, 2007 3:23 pm
Temat: RE: [abinit-forum] non self-consistent kinetic energy
Do: forum@abinit.org

> Hi Ron,
> 
> I am no longer a user of ABINIT although I was in the past.  It 
> may be
> necessary to save a self-consistent potential at the same time 
> that the
> charge density is saved, I am not sure.  I know that we routinely did
> this kind of calculation to compute band structures -- obviously 
> for the
> band structure we wanted a new selection of k-points that had 
> nothing to
> do with the original self-consistent "special points" set.  I 
> think I
> usually saved the potential, but in principle it should be easy to
> compute a potential non-self-consistently from an input density 
> and then
> iterate the wavefunctions to convergence, all non-self-
> consistently.  I
> can't tell you exactly what iscf and other choices you need but 
> surely a
> current user can provide this to you.  The kinetic energy you seek 
> wouldhave to be computed (non-self-consistently) in order to 
> iterate the
> wavefunctions to convergence in that fixed potential, so you would 
> havethe number you seek.
> 
> It may help to look in the help file to see how to compute band
> structures and follow that procedure.
> 
> Best regards,
> Doug  
> 
> -----Original Message-----
> From: Ronald Cohen [mailto:rcohen@ciw.edu] 
> Sent: Tuesday, June 12, 2007 9:34 PM
> To: forum@abinit.org
> Subject: Re: [abinit-forum] non self-consistent kinetic energy
> 
> Yes, exactly. That is what I want to do! So far I have not been 
> able to
> see how to do so.
> 
> Sincerely,
> 
> Ron
> 
> 
> 
> 
> Allan, Douglas C Dr wrote:
> > Dear Xavier and Ron,
> >
> > My reading of Ron's question suggests that he wants a kinetic 
> energy 
> > corresponding with a given charge density that was generated 
> with 
> > wavefunctions at k-points different from the new set.  That is, 
> he 
> > does not have input wavefunctions for the case of interest, he 
> needs 
> > to compute them.  If I am right, then he needs to read the 
> charge 
> > density in and then do a non-self-consistent calculation that is 
> > iterated to convergence in the wavefunctions.  The resulting 
> kinetic 
> > energy should be what he seeks.  I no longer know the proper 
> iscf to
> achieve this.
> > Note that he is not going self-consistent again, but he is 
> iterating 
> > to convergence in the wavefunctions.  This should be possible 
> for any 
> > desired k-point grid whether it makes sense as a self-consistent 
> > special points grid or not.  It is the same method one uses to 
> compute
> > a bandstructure given a charge density.
> >
> > Best regards,
> > Doug
> >
> > -----Original Message-----
> > From: Xavier Gonze [mailto:gonze@pcpm.ucl.ac.be]
> > Sent: Tuesday, June 12, 2007 9:12 AM
> > To: forum@abinit.org
> > Subject: Re: [abinit-forum] non self-consistent kinetic energy
> >
> > Dear Ron,
> >
> > On 12 Jun 2007, at 14:36, Ronald Cohen wrote:
> >
> >   
> >> I am trying to figure out how to get ABINIT to compute and 
> print the 
> >> kinetic energy that corresponds to a  given input  charge 
> density, 
> >> generated with a different k-point set. This is needed to 
> correct QMC
> 
> >> results. It is important to do this  without going self- 
> consistent 
> >> again.With iscf=-3 I get a total energy, but not the kinetic 
> energy.>> In fact, if I print results%ek in the code it is zero. 
> Setting nstep 
> >> to 0 or 1 seems to give nonsense with iscf>0.
> >>
> >> Ronald Cohen
> >>     
> >
> > Well, I would have said that you have to activate evaluation of 
> the 
> > energy components by the routine energy.F90 (you might have a 
> look at 
> > the header of that routine), which corresponds to nstep=0 . In 
> this 
> > case, the energy is evaluated directly from the input wavefunctions.
> > Moreover, there is a test case : Test v1#89 (some of the 
> datasets).  
> > So, I am a bit surprised
> > to see that nstep 0  gives nonsense for you. Could you send the 
> input 
> > file ?
> >
> > Best regards,
> > Xavier
> >
> >   
> 
> 
>
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