Titanium oxide computation

Figure 3.38. Experimental densities of titanium oxides (continuous lines). The upper dotted line gives the values computed for a 100% occupancy of the cation sites in the NaCl structure type (from Hyde and Andersson 1989).

Redfern PC, Zapol P, Curtiss LA, Rajh T, Thumauer MC. Computational studies of catechol and water interactions with titanium oxide nanoparticles. J Phys Chem B 2003 107 11419-27. 

A review of First Principles simulation of oxide surhices is presented, focussing on the interplay between atomic-scale structure and reactivity. Practical aspects of the First Principles method are outlined choice of functional, role of pseudopotential, size of basis, estimation of bulk and surface energies and inclusion of the chemical potential of an ambient. The suitability of various surface models is discussed in terms of planarity, polarity, lateral reconstruction and vertical thickness. These density functional calculations can aid in the interpretation of STM images, as the simulated images for the rutile (110) surface illustrate. Non-stoichiometric reconstructions of this titanium oxide surface are discussed, as well as those of ruthenium oxide, vanadium oxide, silver oxide and alumina (corundum). This demonstrates the link between structure and reactivity in vacuum versus an oxygen-rich atmosphere. This link is also evident for interaction with water, where a survey of relevant ab initio computational work on the reactivity of oxide surfaces is presented. 

The only heteroatom which we consider is H (via adsorption of H2O). As our subject is periodic calculations, amorphous films are outside the scope of this review. The large body of work on adsorption onto titanium oxide of organic molecules or metal nanoparticles is reviewed in Ref [1]. Metals on oxide supports are covered in the chapter by N. Roesch (in this volume). Two related reviews consider the computation of thin films [2] and polar surfaces, especially their reconstruction [3]. Useful overviews of surface science techniques and terminology, as well as historical views of work on metal surfaces, are given in Refs. [4,5]. 

The photocatalytie reduction of henzonitrile to benzylamine has been obtained in aqueous suspensions of Pd loaded titanium oxide. One and two-photon absorption of di- and triphenylamine has been computationally studied. Visible-light mediated heterogeneous C-H functionalization has been obtained by oxidative multicomponent reaction using a recyclable TiOa catalyst, and has been extended to the direct conversion of a sps C-H bond into a The reduction of nitriles... 

A 3/8 inch diameter aluminum or titanium-tungsten dot pattern WLs fabricated on top of the cured polyimide film to make electrical leakage to substrate measurements for pinhole density estimation. An etch decoration technique was used to visually determine pinhole densities in polyimide films. The polyimide film was cast on substrates comprised of a layer of 200 nm thick alumimmi on blue colored field oxide with a grid pattern for area computation. Replicate holes were etched in the aluminum by a hot phosphoric acid solution. With the polyimide film removed, a good visual contrast was achieved for pinhole density counting. 

In summary, the TS-1 catalyzed epoxidation of propylene with H2O2 to PO is a thoroughly investigated epoxidation reaction. The oxidation chemistry is well known by now, and the catalyst, and the process parameters have been optimized. Currendy, the titanium-based catalyst is in the process of being commerciahzed. Computational chemistry has been appHed to elucidate the details of the surface chemistry and to identify the important reaction steps at this point, various competing mechanisms, proposed by different authors, can be found in the literature. 

It must be noted that on the solid surface different active sites may have different coordination numbers. The oxidation states of titanium at different sites may also be different. Based on computational studies, the oxidation state of titanium at the active sites is considered to be mainly 4+. 

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