Koch Daniel, Manzhos Sergei
Department of Mechanical Engineering, National University of Singapore , 9 Engineering Drive 1, Singapore 117576, Singapore.
J Phys Chem Lett. 2017 Apr 6;8(7):1593-1598. doi: 10.1021/acs.jpclett.7b00313. Epub 2017 Mar 23.
The oxidation state of titanium in titanium dioxide is commonly assumed to be +4. This assignment is based on the ionic approximation and is used ubiquitously to rationalize phenomena observed with TiO. It implies a charge state +4 and that no further oxidation of the metal center is possible. We present a comprehensive electronic structure investigation of Ti ions, TiO molecules, and TiO bulk crystals using different density functional theory and wave function-based approaches, which shows that the charge state of Ti is +3. Specifically, there is evidence of a significant remaining contribution from valence s and d electrons of Ti, including the presence of a nuclear cusp around the Ti core. The charge corresponding to valence s and d states of Ti amounts to 1 e. This suggests the possibility of further oxidation of Ti in TiO compounds and challenges the commonly assumed picture of assigning the oxidation state of Ti in titania to +4.
二氧化钛中钛的氧化态通常被认为是 +4。这一认定基于离子近似法，并且被广泛用于解释二氧化钛所观察到的现象。它意味着电荷态为 +4，且金属中心不可能进一步氧化。我们使用不同的密度泛函理论和基于波函数的方法，对钛离子、TiO 分子和 TiO 块状晶体进行了全面的电子结构研究，结果表明钛的电荷态为 +3。具体而言，有证据表明钛的价 s 电子和 d 电子存在显著的剩余贡献，包括在钛原子核周围存在核尖点。与钛的价 s 态和 d 态对应的电荷为 1 个电子。这表明在 TiO 化合物中钛有可能进一步氧化，并且挑战了将二氧化钛中钛的氧化态认定为 +4 的普遍观点。
