Hi

A have a few technical questions regarding the coulomb cutoff in 2D. I have been using this for a few systems and it seems to work very well with the random integration method applied to G=(0,0,0). I guess you use the analytical expression from Phys. Rev. B 73, 205119 (2006)?

However, I am a bit curious how it is done since the coulomb potential diverges at q=0 whenever the components of G in the periodic directions vanish. I would thus think that it is nessecary to use the RIM method for all the G vectors with vanishing components G_p in the parallel direction at q=0. On the other hand, it seems to me that the divergence can be removed if the cutoff radius R is chosen to be exactly half the non-periodic cell length, since then sin(G_n R)/G_p will vanish for all G vectors (here G_n is the component of G in the non-periodic direction). Is this a good way to circumvent these divergences or is it problematic to make this choice and ignore the inherent divergence at G_p=0. In my calculations I have not chosen the cutoff to be exactly half the cell length (but close by) so I would think the divergence is there, but it works fine. How does Yambo do it?

BR

Thomas Olsen

Post Doc

Technical University of Denmark