[Pw_forum] Electrons kinetic energy
Pietro Bonfa'
pietro.bonfa at fis.unipr.it
Wed Oct 16 17:04:19 CEST 2013
Dear All,
following the recipes given in this thread:
http://qe-forge.org/pipermail/pw_forum/2009-May/087347.html
I added two routines to the pp.x code to calculate the average
electronic kinetic energy. I started from both the elf.f90 subroutine in
PP code and from the pw2casino implementation.
It's almost only a matter of copy/paste but there is a thing I cannot
understand.
Let "kkin" be the variable with the kinetic energy density, following
the elf.f90 code I have:
0 ! symmetrize the local kinetic energy if needed
1 IF ( .not. gamma_only) THEN
2 !
3 CALL sym_rho_init ( gamma_only )
4 !
5 aux(:) = cmplx ( kkin (:), 0.0_dp, kind=dp)
6 CALL fwfft ('Dense', aux, dfftp)
7 ALLOCATE (aux2(ngm))
8 aux2(:) = aux(nl(:))
9 !
10 ! aux2 contains the local kinetic energy in G-space to be
symmetrized
11 !
12 CALL sym_rho ( 1, aux2 )
13 !
14 aux(:) = (0.0_dp, 0.0_dp)
15 aux(nl(:)) = aux2(:)
16 DEALLOCATE (aux2)
17
18 CALL invfft ('Dense', aux, dfftp)
19 kkin (:) = dble(aux(:))
20 !
21 ENDIF
22 T = sum( kkin(:) )*omega / ( dfftp%nr1*dfftp%nr2*dfftp%nr3 )
To get the correct kinetic energy (T), with respect to elf.f90, I had to
change
CALL fwfft ('Smooth', aux, dfftp)
to
CALL fwfft ('Dense', aux, dfftp)
on line 6 because otherwise I couldn't perform the sum correctly (even
if using dffts%nr1 nr2 nr3).
With this trick the elf-derived and the pw2casino-derived routines give
similar results in all the cases I used for testing.
Nonetheless, I'm completely unfamiliar with the QE implementation, and
probably there is no need to change Smooth to Dense.
Moreover, I don't really know if performing sym_rho on the Dense grid is
fine or not.
Can someone please help me figure out my mistake(s)?
Thanks,
Pietro
ps: the subroutines are attached.
--
Pietro Bonfa' - PhD student
Dipartimento di Fisica e Scienze della Terra "Macedonio Melloni"
Viale delle Scienze 7A
43124 Parma - Italy
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