The ABINIT Users Mailing List ( CLOSED )

["Matteo Giantomassi" <Matteo.Giantomassi@uclouvain.be>]

> You have to do this by hand for the moment. The idea is that for each mode
> you calculate the contribution in the phonon eigenvectors (normalized)
> which
> is due to a given atom, e.g.
>
> weight(lambda, q, tau) = sum_i  |u_lambda,q (i, tau)|^2
>
> for direction i, atom tau, phonon mode lambda and qpoint q. The sum of
> these
> over all tau gives 1 (for a given lambda,q), so you have a weight.
> Multiply
> this by the phonon dos, and you get a PDOS. This also works fine for
> crystals and any other system.
>
> PDOS_tau (omega) = sum_q,lambda  weight(lambda, q, tau)
> delta(omega-omega_q,lambda)
>
> It should be fairly easy to add this to the anaddb output at some point -
> someone may even have already done it! I notice Matteo Giantomassi has a
> routine mkphdos with similar functionality: Matteo does this work yet?

 Hi Matthieu,

 Well, it should work but some hacking is needed to enter this part of the
code (see below)
 I wrote the routine some time ago and I've used it for one of my
 applications. It provides the PHDOS calculated either with tetrahedrons or
 standard gaussian smearing. Type-projected contributions to the total PHDOS
 are also available.
 Atom-projected contributions are not directly available because the
different
 contributions arising from atoms of the same type are summed up.
 Anyway calculating atom-projected contributions is just a matter of
changing a bit the routine (17ddb/mkphdos.F90).

 No example and reference output files are provided yet (I know, I know,
shame on me!).
 Digging into my files I found an anaddb input that can be used to
calculate the PHDOS,
 The flags that have to be added in the input file are:

ifcflag  1  #IFC's are needed

#DOS related variables
prtdos  1              # 1 for gaussian, 2 for tetrahedrons
ng2qpt  35 35 7        # Dense q-mesh for Fourier interpolation
q2shft  0.0 0.0 0.0    # Shift for the dense mesh
dosdeltae  9.112670E-7 # 0.1 cm-1  frequency step for PHDOS
dosmear    1.366900E-5 # 3 cm-1    broadening (only for Gaussian method)

At the end of the calculation the results are stored in the PHDOS file
There are several columns:

 # omega     PHDOS    IPHDOS   PJDOS[1]  IPJDOS[1] ..

 PHDOS refers to the total phonon DOS, IPHDOS is the integrated DOS, then
we have the
 contribution due to all the atoms of the first type as well as the
corresponding integrated dos.

3 Comments:

1) To call mkphdos you have to modify a bit 17ddb/invars9
  commenting out the call to leave_new in the following piece of code

 if(anaddb_dtset%prtdos/=0 .and. anaddb_dtset%ifcflag/=1) then
  write(message, '(5a)' )&
&  ' invars9 : ERROR -',ch10,&
&  '  ifcflag must be 1 when the calculation of the phonon DOS is required
',ch10,&
&  '  Action : correct ifcflag in your input file.'
  call wrtout(6,message,'COLL')
  call leave_new('COLL')
 end if


2) If I remember well in old versions of abinit there's a small bug (just
a missing factor)
   in the calculation of the integrated type-projected PHDOS. So don't
rely on the columns
   reporting the type-projected IPHDOS. If you need, you can easily
integrate the curve using
   a plotting software such as xmgrace.

3) Be careful when using the tetrahedron method. The CPU time doesn't
scale well wrt
   to the number of Fourier interpolated q-points. This is a general
problem I found also
   in case of electronic DOS calculations. One should do some serious
profiling of the tetrahedron
   routines and the fortran loops to individuate the bottleneck.

Hope it helps.
Best Regards
Matteo Giantomassi