Extended homologous series of Sn-O layered systems: a first-principles study

TL;DR

This study predicts new intermediate Sn-O compounds between SnO and SnO2, analyzes their electronic properties, and highlights the importance of van der Waals interactions in their structural modeling.

Contribution

It introduces several new Sn-O compounds with intermediate oxygen concentrations and compares different computational functionals for accurate property predictions.

Findings

New intermediate Sn-O compounds predicted between SnO and SnO2.

Band gap decreases with increasing oxygen content and SnO-like units.

van der Waals interactions significantly affect structural and electronic calculations.

Abstract

Apart from the most studied tin-oxide compounds, SnO and SnO2, intermediate states have been claimed to exist for more than a hundred years. In addition to the known homologous series (Seko et al., Phys. Rev. Lett. 100, 045702 (2008)), we here predict the existence of several new compounds with an O concentration between 50 % (SnO) and 67 % (SnO2). All these intermediate compounds are constructed from removing one or more (101) oxygen layers of SnO2. Since the van der Waals (vdW) interaction is known to be important for the Sn-Sn interlayer distances, we use a vdW-corrected functional, and compare these results with results obtained with PBE and hybrid functionals. We present the electronic properties of the intermediate structures and we observe a decrease of the band gap when (i) the O concentration increases and (ii) more SnO-like units are present for a given concentration. The contribution of the different atoms to the valence and conduction band is also investigated.