The ABINIT Users Mailing List ( CLOSED )

["Allan, Douglas C Dr" <AllanDC@corning.com>]

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 would
have to be computed (non-self-consistently) in order to iterate the
wavefunctions to convergence in that fixed potential, so you would have
the 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
>
>