NaN in TDDFT calculation with yambo 4.2.1

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javad
Posts: 34
Joined: Fri Feb 28, 2014 10:23 pm

NaN in TDDFT calculation with yambo 4.2.1

Post by javad » Fri Dec 15, 2017 4:24 pm

Dear people of yambo

I get NaN when I perform ALDA with yambo on a simple molecule
here my input files

with the best regards
Javad
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Javad Exirifard
IPM - Institute for Research in Fundamental Sciences
P. O. Box 19395-5746
Niavaran Square
Tehran, Iran

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Daniele Varsano
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Re: NaN in TDDFT calculation with yambo 4.2.1

Post by Daniele Varsano » Sat Dec 16, 2017 4:27 pm

Dear Javad,
can you also add the report file of your calculation?
In any case my suggestion is to evaluate the TDDFT ALDA in configuration space more than in G space, as in G space you can have instability in the region of low density.
In order to do that you need to build the input as:
yambo -o b -k alda -y d
In this way you have also the advantage to include automatically all the G vectors in the kernel.
Best,
Daniele
Dr. Daniele Varsano
S3-CNR Institute of Nanoscience and MaX Center, Italy
MaX - Materials design at the Exascale
http://www.nano.cnr.it
http://www.max-centre.eu/

Jiuyusun
Posts: 1
Joined: Sat Sep 19, 2015 6:32 am

Re: NaN in TDDFT calculation with yambo 4.2.1

Post by Jiuyusun » Fri Apr 03, 2020 11:21 pm

Hi Daniele,

I am interested in:
Daniele Varsano wrote:
Sat Dec 16, 2017 4:27 pm
In any case my suggestion is to evaluate the TDDFT ALDA in configuration space more than in G space, as in G space you can have instability in the region of low density.
I notice you had said this kind of suggestion several times in the form. Why ALDA in G space is less stable? Can you refer me some references about this issue?

Thanks
Jiuyu
Jiuyu Sun
Department of Physics
University of Missouri, Columbia, MO, USA.

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Daniele Varsano
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Joined: Tue Mar 17, 2009 2:23 pm
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Re: NaN in TDDFT calculation with yambo 4.2.1

Post by Daniele Varsano » Sat Apr 04, 2020 6:00 am

Dear Jiuyu Sun,
for a long time now Yambo has been using the libxc libraries to evaluate the kernel, and therefore I would say that instabilities problem are no longer present. Main difference in the two approaches is that in G-space you include a number of kernel components equal to the block considered in the response function, while in transition space the kernel is evaluated in real space and all the components are automatically considered.

Best,
Daniele
Dr. Daniele Varsano
S3-CNR Institute of Nanoscience and MaX Center, Italy
MaX - Materials design at the Exascale
http://www.nano.cnr.it
http://www.max-centre.eu/

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