Lawrence Berkeley National Laboratory

Based on first-principles calculations, we predict a substantial increase in the optical dielectric function of LiAsSe2 under pressure. We find that the optical dielectric constant is enhanced threefold under compression along all three axes by 3%. This enhancement is mainly due to the dimerization strength reduction of the one-dimensional (1D) As-Se chains in LiAsSe2, which significantly alters the wave function phase mismatch between two neighboring chains and changes the transition intensity. By developing a tight-binding model of the interacting 1D chains, the essential features of the low-energy electronic structure of LiAsSe2 are captured. Our findings are important for understanding the fundamental physics of LiAsSe2 and provide a feasible way to enhance the material optical response that can be applied to light harvesting for energy applications.