A strategy for optical properties investigation in ABe2BO3F2 (A=K, Rb, Cs) using finite field methods

The finite-field methods can be used to intuitively learn about the optical response and find out the atomic contributions to the birefringence and SHG tensors. In this paper, the linear and second-order nonlinear optical properties of ABe2BO3F2 family (A = K, Rb, Cs) compounds are investigated using the finite-field methods within different exchange-correlation functionals. The results show that the obtained birefringence and SHG tensors are in good agreement with the experimental values. The atomic contribution to the total birefringence was further investigated using the variation of the atomic charges, and the Born effective charges. The results show that the boron-oxygen groups give main contribution to the anisotropic birefringence.