Input variables of yambo_rt

[Davide Sangalli]

Dear Chenhai Shen,
you need to set:

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Field1_kind= "DELTA" # [RT Field1] Kind(SIN|RES|ANTIRES|GAUSS|DELTA|QSSIN)
Field1_pol= "linear" # [RT Field1] Pol(linear|circular)

and a small value for

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Field1_Int= 0.000000 kWLm2 # [RT Field1] Intensity

What is "small" depends on the system. You can try with 1.E4 for a start.

Moreover

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% Field1_Dir
1.000000 | 0.000000 | 0.000000 | # [RT Field1] Versor
%

defines the direction along which the dielectric function is computed.
Setting the "x" direction as above, ypp_rt will then reconstruct eps_{xi} with i={x,y,z}

You should also see variables which define the number of bands included in the calculation and the kind of approximation you would like to use.
Few info can be found here (section VII):
https://arxiv.org/abs/1902.03837

Best,
D.

[Davide Sangalli]

Dear Chenhai Shen,
following the indication in the previous message you will be able to reconstruct the absorption spectrum when light is linearly polarized.
Just run as a first step

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yambo_rt -n p -v sex

and then

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ypp_rt -t X

On the other hand you can run simulations with circularly polarized light.
You just need to set

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Field1_pol= "circular" # [RT Field1] Pol(linear|circular)

and

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% Field1_Dir
 1.000000 | 0.000000 | 0.000000 |        # [RT Field1] Versor
%
% Field1_Dir_circ
 0.000000 | 1.000000 | 0.000000 |        # [RT Field1] Versor_circ
%

for a field circularly polarized in the xy plane.
However we did not code yet the expression to reconstruct the absorption spectrum.

[Davide Sangalli]

1.

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Field1_Width= 0.000000 fs # [RT Field1] Width

What is the physical meaning of this parameter and how should it be set?

It is the pulse duration in case you select "GAUSS" or "QSSIN" in point 2

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Field1_kind= "DELTA" # [RT Field1] Kind(SIN|RES|ANTIRES|GAUSS|DELTA|QSSIN)

How to set this parameter when calculating circularly polarized light?

It is the kind if pulse in the simulation.
- "DELTA" is a "Dirac Delta in time" pulse and is usually what you want to compute absorption
- "SIN", "RES" and "ANTIRES" are pulses which oscillate in time at a specific frequency
- "GAUSS" is a gaussian in time
- "QSSIN" is a pulse with a Gaussian profile in time, convoluted with a function oscillating at a specific frequency

The circular polarization is constructed using two linearly polarized pulses shifted in time by T/4 (here T=2pi/omega is the period)
It is meaningful only for the pulses where a frequency is defined: "SIN", "RES" "ANTIRES", "QSSIN"
It is ignored otherwise

3.How to set the left and right circularly polarized light, separately?

One option is to set for left

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% Field1_Dir
  1.000000 | 0.000000 | 0.000000 |        # [RT Field1] Versor
%
% Field1_Dir_circ
  0.000000 | 1.000000 | 0.000000 |        # [RT Field1] Versor_circ
%

and for right

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% Field1_Dir
  1.000000 | 0.000000 | 0.000000 |        # [RT Field1] Versor
%
% Field1_Dir_circ
  0.000000 | -1.000000 | 0.000000 |        # [RT Field1] Versor_circ
%

or

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% Field1_Dir
  0.000000 | 1.000000 | 0.000000 |        # [RT Field1] Versor
%
% Field1_Dir_circ
  1.000000 | 0.000000 | 0.000000 |        # [RT Field1] Versor_circ
%

(I could have reversed left and right, please check)