Li₃GaTe₄O₁₁: small ion-driven orientation of TeO_n units in a tunnel-structured tellurite

In Li₃GaTe₄O₁₁, asymmetric TeO_n (n = 3, 4) polyhedra and GaO₆ octahedra form a three-dimensional (3D) tunnel framework, with Li⁺ cations occupying the sixteen-membered channels. The high framework density (12.1) and small void space (3.75%) of Li₃GaTe₄O₁₁ collectively demonstrate that Li⁺ cations are spatially confined within the tunnels by the dense, compact framework. This confinement amplifies their steric influence, thereby enabling effective regulation of TeO_n (n = 3, 4) with large local dipole moments. The real-space projections of the valence band maximum (VBM) and conduction band minimum (CBM) also reveal that small interstitial Li⁺ cations can act as "structural mediators" to tune the arrangement of TeO_n (n = 3, 4) units, thereby influencing the framework of Li₃GaTe₄O₁₁. This work opens a new avenue for exploring non-centrosymmetric (NCS) materials through resident cation engineering.