2D cut-off for SHG

[sunxl]

Dear all，

1、When calculating the nonlinear properties of two-dimensional materials, -r needs to be added. Is it added after removing the symmetry? For example, when I calculate SHG of BSE, I need to add "-r" to the input file of Collision step and SHG step respectively, is that right?

2、For the calculation of absorption spectra, second-order nonlinear effects and GW energy bands, when I converge all the input parameters with very few k points, can I still use the parameters that have been converged before when I change to a large k point? Or do we need to retest convergence? In other words, as the number of k points increases, does the convergence change for the input parameters in the above calculation?

Best,
sunxl

[claudio]

Dear Dr. sunxl

> 1、When calculating the nonlinear properties of two-dimensional materials, -r needs to be added. Is it added after removing the symmetry? For example, when I calculate SHG of BSE, I need to add "-r" to the input file of Collision step and SHG step respectively, is that right?

yes, you have to use it in the calculation of collisions

> 2、For the calculation of absorption spectra, second-order nonlinear effects and GW energy bands, when I converge all the input parameters with very few k points, can I still use the parameters that have been converged before when I change to a large k point? Or do we need to retest convergence? In other words, as the number of k points increases, does the convergence change for the input parameters in the above calculation?

in my opinion you can use the same parameters you found with few k-points for the calculation with larger k-points

best
Claudio