### Oddness of Imaginary Dielectric Function

Posted:

**Tue Sep 24, 2019 7:38 am**Dear developers,

As required by its oddness, we know that the imaginary part of dielectric function strictly vanishes at ω=0.

Indeed, that's what we get in an IP spectra calculation of Yambo.

However, I was confused that the usually used expression, as given in Eq.(1) of https://iopscience.iop.org/article/10.1 ... 48X/ab15d0, seems not to guarantee the oddness. I.e., the Eq.(1) can't ensure a strictly-zero-value at ω=0, since a finite broadening of spectrum will lead to an accumulation of intensity at ω=0.

Thus, I'd like to know if Yambo had use any technical approaches or additional constraints to ensure the imaginary dielectric function to be strictly zero at ω=0.

Thank you very much,

As required by its oddness, we know that the imaginary part of dielectric function strictly vanishes at ω=0.

Indeed, that's what we get in an IP spectra calculation of Yambo.

However, I was confused that the usually used expression, as given in Eq.(1) of https://iopscience.iop.org/article/10.1 ... 48X/ab15d0, seems not to guarantee the oddness. I.e., the Eq.(1) can't ensure a strictly-zero-value at ω=0, since a finite broadening of spectrum will lead to an accumulation of intensity at ω=0.

Thus, I'd like to know if Yambo had use any technical approaches or additional constraints to ensure the imaginary dielectric function to be strictly zero at ω=0.

Thank you very much,