The ABINIT Users Mailing List ( CLOSED )

[Marek Veithen <Marek.Veithen@ulg.ac.be>]

xhongjun wrote:

Dear abinitioners,
     Can the  ABINIT v4.0.3 code calculate the Raman activities?
     I know the Raman cross-section is implemented and I should contact
    M. Veithen if I want to use these features.But I don't know how to
contact M. Veithen.I hope somebody can tell me M. Veithen's E-mail.

Thanks

xianghjun

Dear Xianghjun,

I am implementing the computation of Raman activities of zone-center
optical phonons as well as the non-linear optical tensor d_ijk
into the ABINIT code.

These features work properly within ABINITv4.0.3
at least for uniaxial crystals and pseudopotentials without non-linear core correction.
You should have a look at the test t83 in the Test_v3 directory to
get an idea of how the computaion of third-order energies works.
It might also be interesting for you
to read the slides of my communication at the ABINIT workshop
that are available at the community webpage

 http://cst-www.nrl.navy.mil/~erwin/abinit/workshop02/presentations/

If you are intended to use the non-linear repsonse part of ABINIT
in a systematic way, than I suggest
you not to use ABINITv4.0.3 as it is available on the web page but I
will send you a beta version of the code I am working on at the moment.

In fact, the computation of third-order energies is not very optimized within
ABINITv4.0.3. For example, the non-linear response part does not take
into account the symmetry operations to reduce the number of perturbations
that have to be computed explicitely. This makes the calculations
quite cumbersome. Moreover, at the stage of ABINITv4.0.3, the code only computes
the "bare" third-order energies and you have to perform all transformations by hand
to get the relevant physical quantities.

The version I am working on at the moment presents some additional features
that make the computation of third order energies more efficient and
allow an easier analysis of the results. In particular it presents
the following caracteristics

    * Use of symmetry operations;
    * Direct output of d_ijk + first-order changes of the dielectric tensor due to individual
       atomic displacements;
    * Output of third-order energies into a DDB that can be merged with a DDB of
        the linear response part and analysed with ANALDDB (IFC).

These features will probably be available within ABINITv4.1 but
I can send you a beta version if you are interested.

Best regards,

Marek
 

-- 
Marek VEITHEN
Universite de Liege
Institut de Physique, Bat. B5
Allee du 6 aout, 17
B- 4000 Sart Tilman
BELGIUM

Phone : ++(32) (0)4-366.36.12
Fax   : ++(32) (0)4-366.29.90
E-mail: Marek.Veithen@ulg.ac.be