External electric field in RT-TDDFT
Clicked A Few Times
2:35:27 PM PST - Wed, Jan 11th 2017
Dear NWChem developers and users,
I am a beginner of the NWChem.
My purpose is to calculate the field emission current from the surface of the carbon related materials e.g., graphite, graphene or carbon nanotubes using the RT-TDDFT of NWChem under the external electric field.
NWChem has four kinds of field types; kick, gpulse, hpulse, and resonant.
However I would like to use another type of field. This type of field is trapezoidal. It has a rise time from 0 to t1 and a fall time from t2 to t3. The plateau is between t1 and t2.
By the NWChem Manual; Release66:NWchem Documentation, page 165, it is shown that “others would have to be manually coded.”
Now I am searching the examples of the input method of the trapezoidal wave. However I could not find the example.
If anyone has examples or references regarding the input method of trapezoidal wave, please teach me.
Thank you.

Toshiharu Higuchi
Yokohama, Japan

Forum Regular
7:12:57 AM PST - Thu, Jan 12th 2017
That comment means that you would have to modify the source code in order to add a different type of field other than the ones that are specified in the documentation.

Clicked A Few Times
4:13:02 PM PST - Thu, Jan 12th 2017
Dr. Sean,
thank you very much for your quickly reply.
I would like to modify the source code in order to add a field of trapezoidal type.
However I do not have an experience to modify the source code.
Is it very difficult?
Thank you.

Toshiharu Higuchi
Yokohama, Japan

Forum Regular
6:58:49 AM PST - Fri, Jan 13th 2017
If you are at least familiar with Fortran, then it should not be too difficult. The part of the code you would need to modify would probably be the rt_tddft_update_fields subroutine in the file $NWCHEM_TOP/src/nwdft/rt_tddft/rtutils/rt_tddft_excite.F

Clicked A Few Times
6:43:14 PM PST - Fri, Jan 13th 2017
Dear Dr. Sean,
thank you for your kind reply.
I will try to modify the subroutine.
I am not a familiar with Fortran, so it will take a long time.
Thank you again.

Toshiharu Higuchi
Yokohama, Japan


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