Ab initio engineering of materials with stacked hexagonal tin frameworks

The group-IV tin has been hypothesized to possess intriguing electronic properties in an atom-thick hexagonal form. An attractive pathway of producing sizable 2D crystallites of tin is based on deintercalation of bulk compounds with suitable tin frameworks. Here, we have identified a new synthesizable metal distannide, NaSn₂, with a 3D stacking of flat hexagonal layers and examined a known compound, BaSn₂, with buckled hexagonal layers. Our ab initio results illustrate that despite being an exception to the 8-electron rule, NaSn₂ should form under pressures easily achievable in multi-anvil cells and remain (meta)stable under ambient conditions. Based on calculated Z₂ invariants, the predicted NaSn₂ may display topologically non-trivial behavior and the known BaSn₂ could be a strong topological insulator.