Dear Roberto,
please note that some bug fixes and other minor changes have been
recently (past few months) included in espilon. I would then
recommend to refer to espresso-5.4.0 for both discussions and actual runs
take care
Andrea
I was reading through the epsilon.f90 code and I noticed that (5.2.1 version) at
line 420 we have the following condition
IF (abs(focc(iband2,ik)-focc(iband1,ik))< 1e-3) CYCLE
this basically means that the contribution to the dielectric function due to
the transitions between
iband2 and iband1 is neglected if the two states have nearly the same
occupation. I removed this
condition and noticed that, in some test case, states close to the Fermi level
and closely spaced in energy would otherwise
contribute a huge amount. This seems to be due to the fact that the denominator
of eq. 10 ( epsilon.x manual ) becomes close
to zero.
I would like to ask experts of pwscf and epsilon.x, in particular, if the CYCLE
condition was introduced for any specific
physical or numerical reason and why it is safe to proceed this way.
Thank you very much for your attention and have a nice day.
Roberto Gaspari
Ph.D.
Compunet-Istituto Italiano di Tecnologia
--
Andrea Ferretti, PhD
S3 Center, Istituto Nanoscienze, CNR
via Campi 213/A, 41125, Modena, Italy
Tel: +39 059 2055322; Skype: andrea_ferretti
URL: http://www.nano.cnr.it
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