Etude ab initio des composés Na2MGe2Q6 (M = Cd, Zn, Hg ; Q = S, Se), Na2ZnSi2S6 et Na2ZnSn2S6 pour optique non linéaire.

Abstract

In this study, we conducted first principles calculations within the density functional theory framework in order to understand the origins of the bonding, electronic, and optical properties of Na2MGe2Q6 (M=Cd, Zn, Hg ; Q=S, Se), Na2ZnSi2S6, and Na2ZnSn2S6 compounds. We analyzed the sensitivity of replacing cations and anions with different electronegativity, which was rationalized in terms of the electronic structure and the contributions of different orbitals. Our calculations yielded lattice parameters, band gaps, dipole moments, and second harmonic components that generally agreed well with the available experimental data. In addition, the electron localization function and atom-in-molecule topological formalisms were used to obtain further insights into the bonding properties. The calculations demonstrated a good concordance between the nature of the analyzed electronic domains and the response to second harmonic generation for the compounds studied. Moreover, the optical properties of these materials were found to be highly sensitive to the combined effects of the [Si/Ge/SnQ4] and [MQ4] units.