Low-temperature structural evolution and possible charge/orbital ordering in orthorhombic Li₂V₃GaO₈

Li₂V₃GaO₈ adopts an orthorhombic spinel-derived structure(Pmma,a = 5.8583 Å,b = 5.7899 Å,c = 8.3854 Å,V = 284.43 ų). In this framework, the octahedral B-site cations (V/Li) form a topologically pyrochlore network (a three-dimensional array of corner-sharing tetrahedra) that is distorted. Such orthorhombic distortions are well known in spinels and are frequently linked to charge and/or orbital ordering with cooperative lattice effects. The pyrochlore topology is preserved, but bond lengths can split and cation sites become inequivalent, signalling an underlying electronic ordering. In Li₂V₃GaO₈, Li+ and Ga³⁺ are electronically inert, while V exists in a mixed-valence state (+3.33), similar to other V spinels such as LiV₂O₄,AlV₂O₄..., where low-T charge and/or orbital ordering is observed. However, only the V sublattice defines a 2D network. The combination of mixed valence and this network places Li₂V₃GaO₈ firmly withinthe family of spinels prone to subtle symmetry-breaking transitions