Dears,
When i use optical module,it always shows this warning:
*[yangxu@WimaxServer 20110113-10]$ /opt/siesta-3.0-rc2/bin/input <
Graphene-optical.EPSIMG*
* ## 0.000000000000000E+000 19.9999000000000 *
* ## 1*
* ## 0.661800000000000 *
* ## 0.000000000000000E+000*
*Fsum rule is not fulfilled by more than a 20%*
* The dielectric function will be extended*
* to higher energies by enforcing the Fsum rule*
* This will increase the quality of the quantities*
* calculated via the Kramers-Kroning relation*
and here is the explanation of fsum-rule in the optical module:
If the F-sum rule is not fulfilled by an amount larger than
certain percentage specified in the program via the parameter THRESHOLD, the
imaginary part of the dielectric function will be appendedby a tail of the
form:
C/w**p
where C and p are determine to ensure continuity and to enforce the F-sum
rule.This should increase the quality of the quantities determined via
theKramers-Kroning relations, however it is not very sophisticated and in
certaincases it can create pathological problems. Anyway, it can be
easily desactivated by setting THRESHOLD to zero.
What should i do to fulfill the f-sum rule?
Should i reset my parameters in the '.fdf' file(see in the attachment) ?I am looking forward! THX! xiaolin,from ZJU * * * *
graphene.fdf
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