Yambo Community Forum

Posted: **Wed Feb 22, 2023 3:42 pm**

Dear all,

I'm currently testing the Github branch "devel_surf" to compute reflection anisotropy spectra (RAS) for Si(001)-surfaces
and I encountered a weird behavior while using the cutoff feature.

I first calculated the dieletric function using the normal linear responds routine:

Code: Select all

yambo -o c -k h -F test_lr_optics.txt

with

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QpntsRXd 1 | 1 |

Then I did the same using the yambo_surf module:

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yambo_surf -t r -F test_without_cutoff.txt

leaving the cutoff variable commented (see test_without_cutoff.txt).

Afterwards I did

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yambo_surf -t r -F test_with_cutoff.txt

and I uncommented the cutoff variable:

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Cutoff                        # [RAS] Cutoff mode (Uncomment to use)
CutZero= 0.000000                # [RAS] Zero position of cutoff fn (Frac)
CutStep= 1.000000                # [RAS] Width of cutoff function (Frac)

(see test_with_cutoff.txt)

In the end I plotted the resulting dieletric functions along the x-axis for all three calculation and compared them to
my previous VASP results (see eps_cmp.pdf). You can see that the VASP results match the ones from YAMBO very well
as long as the cutoff is disabled. With the cutoff varibles set to 0 and 1 I would assume that I would obtain the same result,
as we filter the whole unit cell but the resulting dielectric function does not match the previous calculation at all.

Did I use the cutoff in the wrong way or am I missing something else?

Thanks you for your help and support!

Best regards,
Max

Posted: **Wed Feb 22, 2023 7:34 pm**

Dear Max,
You're right, the results should be identical. I'll have a look into it.
Conor

Posted: **Fri Feb 24, 2023 9:49 am**

Dear Conor,

I contact Matthias May and the mistake was at my end. I missed an update on the 19.12.2022 on Github and had an older version of the development version installed.
Now everything works as it should.

I apologize for the inconvenience.

Best regards,
Max

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