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Hi everyone,

I am trying to calculate the second harmonic generation in a 2D material using VASP. However, there is no clear and straightforward guide or examples in the vasp manual for these calculations. I also read many related papers that used vasp to calculate the SHG but I didn't find enough information so that I could actually start my own calculations. So, I am wondering if anyone can help me with this.
Thank you in advance.

Kind regards,
Roma

SHG cannot be calculated with VASP at the moment. You need the second derivative of the polarization with respect to an electric field to get these coefficients. In VASP, many response properties are implemented via finite differences so perhaps this is a possible approach. However, second numerical derivatives commonly suffer from numerical instabilities.

As an alternative, you can contact the authors of one of the papers you mention and ask them whether they have a workflow they would be willing to share with you.

Thank you for letting me know.