The ABINIT Users Mailing List ( CLOSED )

[Ronald Cohen <rcohen@ciw.edu>]

The Kohn-Sham kinetic energy is defined from the occupied wave functions 
for a given Kohn-Sham potential. It does not require self-consistency to 
compute. That is the value I need.

Ron


Pawel Scharoch wrote:
>    Dear colle agues,
>
>      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 wiadomos'c' -----
> 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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