The ABINIT Users Mailing List ( CLOSED )

["Martin Stankovski" <martin.stankovski@uclouvain.be>]

Dear Cheng Daoijan,

The PAWDEN density includes the full valence density inside and outside the 
atomic cores. However, since there is a lot of density concentrated in a 
small spatial region near the cores, the standard "sum-over-grid-values" 
(which corresponds to a trapezoid rule integration) can become inaccurate. 
Inside abinit, the density is not represented purely on the fine FFT grid, so 
the calculation is accurate. It is only when the density is interpolated onto 
the fine FFT grid for the output that the problem arises. 

In principle, the density could be rescaled so that the PAWDEN output is 
normalised with respect to the sum over the grid, but this would make the 
values on the grid inaccurate. If you want to convince yourself that the 
output values are the true values of the density, you need to make a 
convergence study with respect to the fine FFT grid (or maybe use a 
higher-order integration rule). The density of the fine grid can be increased 
by setting higher values in the keyword "pawecutdg" or by controlling the 
fine FFT grid directly through "ngfftdg"

Hope this helps,
Best regards,
Martin Stankovski


-----Original Message-----
From: Daojian Cheng [mailto:chengdaojian@gmail.com] 
Sent: den 4 januari 2010 14:14
To: forum@abinit.org
Subject: [abinit-forum] AIM problem

Dear Abinit users,

Using AIM to compute atomic charges for a spin polarised PAW calculation
(nspden 2), I used the PAWDEN file with AIM. However, I obtained a total 
number
of electrons that is lower than expected, i.e. it does not sum up to the 
number
of valence electrons in the pseudopotentials. However, I made the same
calculation with the DEN file but this time the results were reasonable. Do 
you
have some experience about the difference between DEN and PAWDEN file using
Abinit 5.8.4?  

I found the same question in the Abinit forum "I know that the DEN file stores
the information for a spin polarised calculation in two columns : the total
density and the spin up density. Is it the same for the PAWDEN file?"  But
there is no answer until now. Do you know something about it? 


Thank you very much for your help. Have a good day!     

With Regards
Cheng Daojian
chengdaojian@gmail.com
2009-1-4
----------------------------------------
Address: Physique des Solides Irradiés et des Nanostructures, 
CP234, Université Libre de Bruxelles, Bd Du Triomphe, B-1050 Bruxelles,
Belgium
tel +32-2-650.57.36, fax +32-2-650.52.27
E-mail: chengdaojian@gmail.com; dcheng@ulb.ac.be
Office: Campus de la Plaine, Bat. NO, niveau 3 
CP234, Université Libre de Bruxelles, Bd Du Triomphe, B-1050 Bruxelles,
Belgium 
----------------------------------------
No virus found in this incoming message.
Checked by AVG - www.avg.com 
Version: 9.0.725 / Virus Database: 270.14.124/2598 - Release Date: 01/03/10 
10:41:00