Drastic changes of electronic structure and crystal chemistry upon oxidation of SnII2TiO4E2 into SnIV2TiO6: an ab initio study

TL;DR

This study uses ab initio calculations to analyze how oxidation transforms Sn2TiO4 into Sn2TiO6, causing significant electronic and structural changes, including increased band gap and bulk modulus.

Contribution

It provides a detailed theoretical explanation of the electronic and crystal chemistry changes during oxidation of Sn2TiO4 to Sn2TiO6, supported by DFT calculations.

Findings

Band gap increases from ~1 eV to 2.2 eV upon oxidation.

Bulk modulus increases by 1.5 times, indicating a shift to more ionic bonding.

Destabilization of SnII leads to formation of rutile Sn2TiO6.

Abstract

From DFT based calculations establishing energy-volume equations of state and electron localization mapping, the electronic structure and crystal chemistry changes from Sn2TiO4 to Sn2TiO6 by oxidation are rationalized; the key effect being the destabilization of divalent tin SnII towards tetravalent state SnIV leading to rutile Sn2TiO6 as experimentally observed. The subsequent electronic structure change is highlighted in the relative change of the electronic band gap which increases from ~1eV up to 2.2 eV and the 1.5 times increase of the bulk modulus assigned to the change from covalently SnII based compound to the more ionic SnIV one. Such trends are also confronted with the relevant properties of black SnIIO characterized by very small band gap.