From micro-to macroscopic: Understanding optical properties in zinc-blend-derived materials Cu2ZnYX4(X = S, Se, Te, Y = Si, Ge, Sn) by means of the quantum chemical topology analysis

• Electron localization function (ELF) has been used to analyze bonding properties.
• Elastic constant of 18 compounds have been calculated.
• Second harmonic generation calculation are found promised for technologic applications.
• Analyzes confirm that the lone pair S–Y interaction is the origin of optical properties.
• Dipolar polarization is computed for both lone pair and covalent bonds.

Intensive calculations in the framework of the density functional theory (DFT) scheme have been carried out in order to predict accurately the dynamical stability and electronic properties of the zinc-blend-derived Cu2ZnYX4(X = S, Se, Te, Y = Si, Ge, Sn) compounds. Emphasis is also placed on the optical properties of the defect chalcopyrite compounds. Advantages of the analysis of the topology of the electron localization function (ELF) to provide microscopic point of view of the chemical bonding in solids are illustrated. A relationship between polarization of bonds and origin-independent atomic contributions to electric dipoles in the Cu2ZnYX4(X = S, Se, Te, Y = Si, Ge, Sn) defect chalcopyrite compounds is highlighted. In fact, what makes these compounds most interesting is a rich collection of S–Y long-distance bond paths. The ELF attractors do not systematically localize on the bond midpoint and their localization depends on electronegativity differences between the atoms forming the X–Y bond and on the nature of the chemical environment. Particularly, we show that the charge transfer remains generally the main contribution to the local bond dipole contribution. The compound which exhibits perturbed S lone pair is the more promising for nonlinear optical properties.

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