Accelerating GW in 2D systems

Since Yambo v5.1 it is possible to use an algorithm able to accelerate convergences of GW calculations in two-dimensional systems with respect to the k point sampling.

The method is explained in the paper:

Efficient GW calculations in two-dimensional materials through a stochastic integration of the screened potential

A. Guandalini, P. D'Amico, A. Ferretti and D. Varsano

available at the link: https://arxiv.org/abs/2205.11946

The method makes use of a truncated Coulomb potential in a slab geometry that in Fourier space reads:

[math]\displaystyle{ V_G(q)=\frac{4\pi}{\vert q+G \vert^2}[1-e^{-\vert q_\parallel+G_\parallel\vert L/2}cos[(q_z+G_z)L/2)] }[/math]

where L is the length of the cell in the non-periodic z direction. As the q-grid is 2D, we have [math]\displaystyle{ q_z = 0. }[/math]

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