diople calculation

Deals with issues related to computation of optical spectra, in RPA (-o c) or by solving the Bethe-Salpeter equation (-o b). Includes local field effects, excitons, etc.

Moderators: Davide Sangalli, Daniele Varsano, andrea.ferretti, andrea marini, Conor Hogan, myrta gruning

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Daniele Varsano
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Joined: Tue Mar 17, 2009 2:23 pm

Re: diople calculation

Post by Daniele Varsano » Thu Sep 03, 2020 12:46 pm

Dear Aldo,
the dipoles file can be reused, provided you are considering the same number of bands. Anyway the timing to calculate them should not depend on the run level.
I found a great difference between the case in which I use an already calculated transition dipole matrix (from IP run), where I can push easily to larger values of the response block size (>3 Ry) and the case in which I do a unique calculation, which is of course longer, but I get memory issues if I don't change the job settings.
I do not get this point, if you do an IP calculation the dielectric matrix it is scalar, so you do not have any block size, which is instead taken into account when considering RPA-LF.

2) If you set a box geometry or any other truncation method, the potential does not belong as 1/q^2 anymore so the results are different and it is not just a scaling, anyway the dipoles are not affected by the geometry as they are independent from the coulomb potential.

Dr. Daniele Varsano
S3-CNR Institute of Nanoscience and MaX Center, Italy
MaX - Materials design at the Exascale

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