The ABINIT Users Mailing List ( CLOSED )

[matthieu verstraete <matthieu.jean.verstraete@gmail.com>]

On Fri, Feb 6, 2009 at 9:17 AM, <yelinhui@hotmail.com> wrote:

Dear All,

I have just started looking at ABINIT and see that the code looks quite
powerful. I have the following questions (I apologize if some are too naive but
please forgive me as a newbie):

1. I saw from the usersguide that ABINIT can treat 0D,1D,2D,3D cases. My
question is that whether they are treated just with the usual supercell
approach (with artificial vacuum added), or in the "intrinsic way" (with the
periodic boundary condition at the reduced dimension being indeed discarded) ?

supercell, but there are improved methods to deal with:
1) cutting off the Coulomb potential (not sure this works in the GS case yet, but at least for the GW calculations)
icutcoul, which is unfortunately not properly documented yet.

2) actually treating the boundary conditions differently, and solving the Poisson equation for an isolated system
http://www.abinit.org/Infos_v5.7/input_variables/vargs.html#icoulomb
 

2. By the way, can ABINIT give the work function for a chosen surface in a 2D
calculation?

yes, turn on prt1dm, and you get the potential along the 3 directions of the unit cell, projected in perpendicular planes. Compare the vacuum value with the Fermi energy.
 

3. About the implementation of the finite electric field:

I am talking about the ground-state calculation with an external electric field
rather than the response function calculation of the e-field. Is the external
e-field implemented for the ground state calculation?

Yes, using a Berry phase formula. There should be a part of a tutorial on this in tutorespfn/

4. About GW:

Thanks to Don Hamann for telling me that ABINIT can get the full GW band
structure by the Wannier interpolation approach. Since I haven't seen any
document of how this should be done (I have got version 5.7.2 compiled), could
anybody kindly offer an sample input file for calculating the full GW band
structrue of, say, Silicon, along the high symmetry lines please?

Or, could anybody please just decribe the steps (especially pointing out the
cautions in the input setup) ?

 This is brand new (Don's implementation). There is probably a test, but few people have used it so far, and there is no tutorial yet (patience...)

Besides, is the GW available for spin-polarized case?

yes, and PAW too, but no spinors yet.

 

4. Cut3d:

It is said that cut3d can be used to visualize the 3d wave function (such as
for OpenDX). Is that the full wave function, or the pseudo one, being
visualized ?

pseudo of course. In the PAW case you could try to reconstruct something, but I don't think this is implemented.
 

5. Is the Bethe-Salpeter equation ready or still being planned ?

nothing yet. You should use the interface to other ETSF codes: DP and EXC, or YAMBO to do BSE or sophisticated TDDFT:

      http://www.etsf.eu/resources/software/codes
 

8. Is it possible to do charged-cell calculations (with neutralizing jellium
background) ?

Yes, with the charge input variable. No sophisticated energy correction schemes are implemented, though.
 

I understand that answes to these questions may not be simple. In that case,
could you please just refer me to the papers related to the corresponding
implementations?

this is too long a list, check the abinit publications list:

 http://www.abinit.org/community/?action="search&text=bib

Matthieu

-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Dr. Matthieu Verstraete

European Theoretical Spectroscopy Facility (ETSF) 
Dpto. Fisica de Materiales, 

U. del Pais Vasco,            
Centro Joxe Mari Korta, Av. de Tolosa, 72,   Phone: +34-943018393
E-20018 Donostia-San Sebastian, Spain        Fax  : +34-943018390

Mail : matthieu.jean.verstraete@gmail.com

http://www-users.york.ac.uk/~mjv500