LiBa ₂ GaSi ₂ O ₈ : A Noncentrosymmetric Silicate Exhibiting Wide Transmission Range and Moderate Second Harmonic Generation Response

A new noncentrosymmetric silicate crystal LiBa₂GaSi₂O₈ was successfully synthesized utilizing high-temperature solution method. LiBa₂GaSi₂O₈ crystallizes in the orthorhombic space group <i>Pna</i>2₁ and consists of three tetrahedra, [LiO₄], [GaO₄], and [SiO₄]; the three units are arranged in a one-dimensional plane to form a [LiGa₂Si₂O₁₅] ring structure, which is then connected to adjacent rings to create a pseudolayer structure and finally stacked into a three-dimensional network. The experimental evidence indicates that this compound exhibits excellent thermal stability with an incongruent melting behavior. Moreover, the title compound exhibits relatively well-balanced nonlinear optical properties, characterized by a high second harmonic generation response (1.14 × KDP), a deep-ultraviolet (deep-UV) cutoff edge (190 nm), and a large band gap (5.56 eV). Furthermore, first-principles calculations demonstrate that the optical characteristic of this compound is predominantly influenced by the [SiO₄] tetrahedra. This study provides insight into the structural and optical characteristics of LiBa₂GaSi₂O₈ and deepens our understanding of structure-property relationships in silicate-based optical materials.