As a result, the surface is not charge neutral, but carries a net negative charge since it is oxygen deficient. In ref. This creates a rumpling of 0.3 ± 0.1 Å of the top layer, with a period 6.5 Å, the unit cell length along the 1¯10 direction. Quartz plus anatase make them a popular collection for gems and mineral collectors since these minerals exhibit wonderful lusters. Rutile is a common accessory mineral in high-temperature and high-pressure metamorphic rocks and in igneous rocks. Rutile has a tetragonal unit cell, with unit cell parameters a = b = 4.584 Å, and c = 2.953 Å. Miners extract and separate the valuable minerals – e.g., rutile, zircon, and ilmenite. Data for the reduced SnO2 (110) surface, however, shows no density of occupied states in the gap (Cox et al., 1988; Egdell et al., 1986). Synthetic rutile was first produced in 1948 and is sold under a variety of names. Rutile was first described in 1803 by Abraham Gottlob Werner. There are two kinds of surface cations in the surface unit cell, one of which is five-fold coordinated with one dangling bond. The rutile (100) surface has received considerably less attention than the (110) crystal face. Finely powdered rutile is a brilliant white pigment and is used in paints, plastics, paper, foods, and other applications that call for a bright white color. The physical properties of rutile are often modified using dopants to impart improved photocatalytic activity through improved photo-generated charge carrier separation, altered electronic band structures and improved surface reactivity. Rutile has one of the highest refractive indices at visible wavelengths of any known crystal and also exhibits a particularly large birefringence and high dispersion. Recent photoelectron diffraction (PED) [79] and STM [80, 81] studies have confirmed the micro-facets model, but contradicted the original conclusion that the surface is terminated by oxygen layer. Murray et al. Both anatase and rutile are tetragonal in structure, but the anatase has octahedrons that share four edges forming the four-fold axis. As expected from symmetry, no relaxations occur along [001]. (1994) also compared results between oriented and vicinal surfaces and suggest that the earlier reports of (1×5) and (1×7) reconstructions may have been due to a slight sample miscut. In Fig. [118] is displayed in (b). The rules of autocompensation and creation of non-polar surfaces discussed above (3.1.1 allows a straightforward prediction of the stable surface termination (Fig. The atom types varied in the structural refinement are shown. Small black circles represent Ti and large grey circles O. The TiO2 (110) surface is very stable and a (1×1) LEED pattern can be easily obtained by preparing a sample using the standard annealing-oxidation treatment (Henrich, 1985). Figure 5.10 shows two models of the surface which would yield a (1×1) surface mesh, one created by a simple bulk truncation of the (110) plane leaving rows of so-called bridging oxygen anions and the other with the bridging oxygens removed (Rohrer et al., 1992). A single-crystalline rutile TiO2 (10 0)-oriented) plate (9 × 9 × 0.5 mm, Shinkosha) was pretreated successively overnight with 3% aqueous NH4OH and 1 M aqueous NaOH. 5.3); each oxygen anion has three cation nearest neighbors. In large enough quantities in beach sands, rutile forms an important constituent of heavy minerals and ore deposits. Klein, Cornelis and Cornelius S. Hurlbut, 1985, Manual of Mineralogy, 20th ed., John Wiley and Sons, New York, pp. Rutile is a mineral composed primarily of titanium dioxide (TiO2), and is the most common natural form of TiO2. [5] as follows: Where, A and R are the peak area for major anatase (2θ = 25°) and rutile phase (2θ = 28°), respectively. Asteriated gems are known as "star" gems. There is good agreement in the Ti atom positions, with some significant discrepancy for the relaxation of O atoms. The surface anions, commonly referred to as the "bridging" anions (see Fig. Again, the same number of Ti - > O as O - > Ti need to be broken, as indicated by the line in Fig. Bunjerd Jongsomjit, ... Piyasan Praserthdam, in Studies in Surface Science and Catalysis, 2006. As it has the lowest molecular volume of the three main polymorphs, it is generally the primary titanium bearing phase in most high-pressure metamorphic rocks, chiefly eclogites. The (1×2) phase corresponds to a superlattice of missing bridging oxygen rows with in-plane Ti cations displaced towards the missing row. The detailed synthesis protocol of the nanosized rutile particles has been given previously [22]. A schematic indication of the (110) surface is given in Fig. In the final model, a surface octahedral interstitial site of the O lattice was found to be occupied by a surface titanium atom, with 40% occupancy per (1 × 3) cell. Several theoretical calculations have determined likely relaxations of the (1 × 1) surface [5,40,109,110]. Open circles are anions, filled circles are metal cations. A Philips XL-30 field emission SEM operated at 15 kV and an HITACH HD-2000 STEM operated at 200 kV were used to carry out SEM analyses. N2 adsorption/desorption measurements for both nanosized rutile and the resulted mesoporous TiO2 were conducted on a Micromeritics Gemini system. Substantial relaxations occur along the [010] direction with the two-fold coordinated and the three-fold coordinated oxygen atoms moving in opposite direction of the five-fold and six-fold coordinated Ti atoms.
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