Ordering by cation replacement in the system Na_2−xLi_xGa₇

Abstract

The Zintl–Wade phase Na1Li1Ga7 introduces a novel variant within the MgB12Si2 structure family. The substitution of Na atoms with Li in Na2Ga7 results in a distinct and fully ordered cation arrangement.

The Solubility of Indium in Na2Ga7

“…However, the number and arrangement of cations in the structure family varies. [1][2][3][4] The cation positions identified for the single crystal with composition Na 2 Ga 6.95 In 0.05 can be visualized by cutting the 3D connected structure into puckered 2D layers of icosahedra and six-membered rings perpendicular to [001] (Figure 3a). In MgB 12 Si 2 and Li 2 B 12 Si 2 , the cations solely occupy the hollows between three six-membered rings, and are termed in the following as position C1 (Figure 3b).…”

“…As no clear preference for the cation arrangement exists in terms of lattice energy, structural disorder of the cation positions occurs (Figure 1). [2] In the ternary compound NaLiGa 7 , [4] however, the smaller size of the Li atoms enables an ordered cation arrangement. Therefore, the question arises whether this also works the other way around: triggering cation ordering by expanding the host framework with the larger In atoms rather than reducing the cation size.…”