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<div class="moz-cite-prefix">Dear Fan,<br>
<br>
On 22/11/2015 23:59, Fan Zheng wrote:<br>
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cite="mid:CADx2QJf5FPKLR=QxO4c7yWs8y8WA__9cN-DqidGuT39vQA7s1g@mail.gmail.com"
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<div>Dear all,<br>
<br>
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I have a question about the electron phonon coupling
calculation in the subroutine "elphel" (in the file
elphonon.f90).<br>
<br>
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<div>This subroutine computes <n,k|dV|m,k+q>.
|n,k> is the wavefunction for band "m" with
wavevector "k".<br>
<br>
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<div>First, the program computes <n,k|dV. Then, it is
multiplied by |m,k+q><br>
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<div><br>
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<div>If q=0, it only needs to read to evc as:<br>
...<br>
IF (lgamma) THEN<br>
CALL get_buffer(evc, lrwfc, iuwfc, ikk)<br>
ELSE<br>
CALL get_buffer (evc, lrwfc, iuwfc, ikk)<br>
CALL get_buffer (evq, lrwfc, iuwfc, ikq)<br>
ENDIF<br>
...<br>
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My question is in the q=0 case, array "evq" is used to
multiply the computed <n,k|dV instead of evc. (line
401-406 in version 5.2.1)<br>
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Can anyone explain why "evc" array is not used in q=0 case
for these line (401-406)? <br>
<br>
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<br>
because in allocate_phq there is the following bit<br>
if (lgamma) then<br>
!<br>
! q=0 : evq and igkq are pointers to evc and igk<br>
!<br>
evq => evc<br>
igkq => igk<br>
else<br>
!<br>
! q!=0 : evq, igkq are allocated and calculated at point k+q<br>
!<br>
allocate (evq ( npwx*npol , nbnd))<br>
allocate (igkq ( npwx))<br>
endif<br>
<br>
therefore in the lgamma case evc and evq (and igkq and igk) are the
same.<br>
<br>
best <br>
stefano<br>
<br>
<br>
<blockquote
cite="mid:CADx2QJf5FPKLR=QxO4c7yWs8y8WA__9cN-DqidGuT39vQA7s1g@mail.gmail.com"
type="cite">
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<div>Thanks,<br>
</div>
Fan<br>
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<br>
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