Abstract
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.
Highlights
The morphology of a crystal structure reflects the underlying bonding mechanism and gives indications about material’s potential applications
Tin readily transforms from the semiconducting diamond α-phase to the metallic higher-coordinated β-phase near room temperature while lead adopts the typical metallic fcc structure. Reflective of this stability trend within group IV, graphene was the first material to be produced as a free-standing atom-thick sheet, with silicene[8,9] and germanene[10] synthesized later as single layers deposited on metallic surfaces
Recalling that exfoliation of graphite was the original route to graphene and that sheets of germanane have been obtained through topochemical deintercalation of CaGe2 with HCl15, we have carried out an ab initio search for new synthesizable bulk compounds comprised of hexagonal tin Department of Physics, Applied Physics and Astronomy, Binghamton University, State University of New York, Binghamton, New York 13902-6000, USA. *These authors contributed to this work
Summary
The morphology of a crystal structure reflects the underlying bonding mechanism and gives indications about material’s potential applications. Tin readily transforms from the semiconducting diamond α-phase to the metallic higher-coordinated β-phase near room temperature while lead adopts the typical metallic fcc structure Reflective of this stability trend within group IV, graphene was the first material to be produced as a free-standing atom-thick sheet, with silicene[8,9] and germanene[10] synthesized later as single layers deposited on metallic surfaces. Having established beneficial features for stability of the desired structural motif, we homed in on the Na-Sn binary system in which a new NaSn2 phase is predicted to form under compressions as low as a few GPa as discussed on page 5, remain (meta)stable under ambient conditions, and, to the best of our knowledge, feature the first all-tin stacking of flat hexagonal layers
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