Unit cell rutile lattice

Fig. 29. Schematic representation of the bulk rutile unit cell (lattice parameters are given in the inset for different materials) [15, 150]...

There are two main types of ionic oxides which are empirically formulated MOg. Where the metal ion is large (Th, 0.95 A Ce +, 0.92 A U, 0.89 A) the crystals are built up of fluorite-type unit cells with 8 4 co-ordination. But where the metal ion is smaller (Sn, 0.71 A Ti, 0.68 A) the structure is based on the rutile lattice with 6 3 co-ordination. Other examples of this structure are VOg, RuOg, PbOg and TeOg. The rutile lattice is slightly deformed in MoOg and WOg. 

Magnesium hydride possesses a rutile lattice, (a) Sketch a unit cell of rutile, (b) What are the coordination numbers and geometries of the Mg and H centres in this structure ... 

Vj Fig 14.17 The unit cell of FeSb20g which has a trirutile lattice compare with the rutile unit cell in Figure 5.21. Colour code Sb, yellow Fe, green O, red the edges of the unit cell are defined in yellow. 

Figure 14.17 shows a unit cell of FeSb20g. (a) How is this unit cell related to the rutile lattice type (b) Why can the solid state structure of FeSb20g not be described in terms of a single unit cell of the rutile lattice (c) What is the coordination environment of each atom type (d) Confirm... 

Powder XRD Provides information regarding unit cell, long range order, bonding and lattice. Can be helpful to determine the phase of a material (for example anatase vs rutile for Ti02) and Scherrer eqn can be applied to estimate particle size. 

A unit cell reflects the symmetry of the crystal structure. Thus, an atom at a position (x, y, z) in a unit cell may require the presence of atoms at other positions in order to satisfy the symmetry of the structure. For example, a unit cell with a centre of symmetry will, of necessity, require that an atom at (x,y,z) be paired with an atom at (—x, —y, —z). To avoid long repetitive lists of atom positions in complex structures, crystallographic descriptions usually list only the minimum number of atomic positions which, when combined with the symmetry of the structure, given as the space group, generate all the atom positions in the unit cell. Additionally, the Bravais lattice type and the motif are often specified as well as the number of formula units in the unit cell, written as Z. Thus, in the unit cell of rutile, given above, Z = 2. This means that there are... 

Cr02 has the rutile (Ti02) structure (Figure 6.11). The Cr " ions are located at the corners of the unit cell and there is a distorted CrOe octahedron in the center. The lattice parameters are a = 0.437 nm and c = 0.291 nm. Cr02 does not occur in nature and is usually manufactured by thermal decomposition of CrOs at 500°C under high pressure (>200 MPa) in the presence of water. 

Nuclear spin relaxation measurements were made of single crystals at between 150 and 1500K, under an O partial pressure of latm. The nuclear magnetic resonance spectrum consisted of a doublet which resulted from 2 different orientations of the electric field gradient tensor at 2 different Ti sites in the unit cell of the rutile lattice. The electric field gradient tensor was due to the 6 surrounding q2- ions, which formed a stretched octahedron. From the temporal evolution of the nuclear spin relaxation rate after a step-wise change in the 0 partial pressure, 2 different types of motion of the intrinsic defects were... 

The three pertinent crystal classes are differentiated in Table 6-3 by their unit cell lattice constants. Rutile and priderite have tetragonal unit cells, while pseudobroo-kite has an orthorhombic unit cell. They are more thoroughly characterized in the PDF database ll... 

Reconstruction A reconstruction is characterized by a change in the periodicity of the outer layer. For example, the (1 x 5) reconstruction of the rutile 100 face indicates that the surface unit cell is in registry with the substrate cell but is five times expanded along the b direction. In the ( /ST X. J31)R9° reconstructed a-alumina 0001 face, the lattice parameters are multiplied by along the a and b directions and the surface cell is rotated by 9° with respect to the underlying layers. When a rotation occurs, it is more precise to give the rotation matrix which connects the unreconstructed and reconstructed lattices, but the simple notation given above is still very often used in the literature. 

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