Orthorhombic lattice parameters

The X-ray patterns taken from the two sections of the intermetallic layer adjacent to the Ni phase were also closely comparable, though this layer is visually seen in Fig. 3.13 to consist of three sublayers. One of these sections corresponded to a layer composition of 16.0 at.% Ni and 84.0 at.% Zn, while the other to 19.0 at.% Ni and 81.0 at.% Zn. The experimental interplanar distances were found to be in better agreement with the calculated values from the orthorhombic lattice parameters of =3.3326 nm, b=0.8869 nm and c=1.2499 nm reported by G. Nover and K. Schubert,279 rather than from the cubic lattice parameter =0.892 nm. Moreover, a few diffraction lines, including the strong line corresponding to the interplanar distance 0.207 nm, could not be indexed on the basis of the cubic structure. 

Replacement of Ba by Sr in the case of the La-Ba-Cu-0 system was thus favorable in decreasing aQ and increasing Tc. However the same is not true in the case of the Y-Ba-Cu-0 system. Figure 2 shows the orthorhombic lattice parameters of aQ, bo and cq for (Ba x rx)2 u3 7 f°r x=0 to 0.7. It is clearly seen that these parameters all decrease with Sr composition, x. Figure 3 shows the resistivity vs. temperature of these specimens. Quite unexpectedly from the discussions up to this point, Tc in this particular system decreases with increase in x. Although the difference in these two examples is not clear yet, it should be quite essential in understanding the mechanism of the superconductivity in the both systems. 

Fig. 13 Relationship between orthorhombic (oo, K) and hexagonal (

A positive deviation from Vegard s law in the case of the orthorhombic lattice parameters [20] is mainly due to the change in the lengths of the metal-metal bonds. Inthiscase, some short-range order may appear when a given Sb atom forms with Zn, Cd, and Sb atoms. This occurs near the 50%/50% composition and may be responsible for the extrema in the dependences of various properties on the composition [13]. Thus, the system described is completely at variance with the ideal representations of so lid-solution structures. 

Crystal Structure and Lattice Parameters (nm) Orthorhombic, a = 0.283, b = 0.554, c = 1.1470 Cr3C2 is an intermediate carbide having carbon chains with C-C distance approximately 0.165 nm running through distorted metal lattice where the Cr atoms are at the corners of trigonal prisms and the carbon atoms in the center of the prisms.i li" ... 

The lattice parameters a and b become different during the transition from the tetragonal to the orthorhombic structure. Either a > b or a < b results, depending on the direction of the rotation of the octahedra strands. During the phase transition both directions of rotation occur at random domains appear, in which either a > b or a < b. The obtained crystal is a twinned crystal or twin, consisting of intergrown domains. The twin domains are... 

Figure 8.11 Transformation of a tetragonal crystal, with lattice parameters aT = bT, into a multiply twinned orthorhombic crystal with lattice parameters a0, bQ. The twinned regions are often called domains and the boundaries may occur on a variety of crystallographic planes.

II.A.1.1. X-Ray Diffraction. The X-ray patterns of silicalite-1 and TS-1 demonstrate a change from the monoclinic structure of the former to orthorhombic when Ti4+ is introduced into the silicalite framework (5). The Rietveld analysis of Millini et al. (75) demonstrates a linear dependence of the lattice parameters and unit cell volume on the extent of Ti substitution in silicalite-1 and constitutes confirmatory evidence for the location of Ti in framework positions. Millini and Perego (77) concluded that the upper limit for incorporation of Ti in the TS-1 framework is about 2.5%. 

Figure 24. X-ray diffraction pattern (in the inset the 2D image) of the polyethylene sample recovered by the laser-assisted high-pressure reaction in the pure liquid monomer. The two measured sharp lines nicely fit the polymer diffraction pattern having a orthorhombic cell (Pnam) defined by the lattice parameters reported in the figure.

The results obtained in the present work show that the developed methods can be applied successfully to oblique texture electron diffraction patterns. The program TexPat has been designed to produce accurate lattice parameters and intensities. Indexing oblique texture electron diffraction patterns from structures with S5mrmetry lower than orthorhombic remains quite difficult task due to the geometrical properties of texture patterns. This difficulty is overcome by the introduction of semi-automatic algorithms for the indexing. 

Electron diffraction study indicates that the unit cell is orthorhombic with lattice parameters a = 3.85 A, b = 3.86 A and c = 11.5 A. The [010] plane group of the crystal is pImm [30]. 

Table 18. Lattice parameters for monoclinic (P2i) and orthorhombic Pn2ia) anhydrous tris-glycolates of the lanthanides, [MCHOCH3 COO) 3]...

As Is well known, the shape of MgS0 7H20 Is an orthorhombic crystal with three different lattice parameters(5), 11.86, 11.99, and 6.858. From these values, the shape factor can be calculated as 0.778. This value closely matches the upper lines of Figure 6. If crystals having a shape factor of 0.778 are wanted, the lower values should be raised so that the amplitude becomes more narrow and the... 

Subsequently the transition has been called the Verwey transition and the transition temperature the Verwey temperature Ty. Verwey also guessed that, below Ty, the mobile electrons order as Fe on [110] rows and Fe on [llO] rows of B-site cations to produce a distortion to orthorhombic symmetry with lattice parameters approximately y/2 + 6)ao X (V2 - 6)ao x ao, where 5 is a small fraction and ao is the cubic lattice parameter. Although Bickford was able to confirm that Fc304 is magnetically orthorhombic at temperatures T < Ty, it is now known that the low-temperature structure is in fact monoclinic with lattice parameters V2ao x y/lz x 2ao and that the electronic ordering is more complex than originally proposed by Verwey. 

Orthorhombic crystals are similar to both tetragonal and cubic crystals because their coordinate axes are still orthogonal, but now all the lattice parameters are unequal. There are four types of orthorhombic space lattices simple orthorhombic, face-centered orthorhombic, body-centered orthorhombic, and a type we have not yet encountered, base-centered orthorhombic. The first three types are similar to those we have seen for the cubic and tetragonal systems. The base-centered orthorhombic space lattice has a lattice point (atom) at each comer, as well as a lattice point only on the top and bottom faces (called basal faces). All four orthorhombic space lattices are shown in Figure 1.20. 

Copper acetate was used in Ref. 38 it was noted that if chloride was used instead of acetate, no deposition occurred, and this was attributed to adsorption of chloride on the substrate (Pt). The berzelianite phase with a small amount of umangite impurity was obtained. The composition and phase of the film could be altered by electrochemical cathodic polarization (in an aqueous K2SO4 solution). Initially, there occurred an increase in lattice parameters and decrease in x (Cu2-A Se). With continued polarization, a phase change occurred until eventually only orthorhombic Cui xSe was present in the film. The umangite phase also disappeared, and it was believed that this impurity phase catalyzed the phase transformation. The change in composition during cathodic polarization was attributed to reduction of zerovalent Se to Se, which was dissolved in the solution. Based on the study of Fohner and JeUinek [41] discussed earlier, this explanation can be interpreted as reduction of Sei ( monovalent Se) to Se (divalent Se). 

Fig. 28. Anisotropic thermal expansion of the orthorhombic FeB phase of GdCu obtained from neutron diffraction experiments on a bulk polycrystalline sample (Blanco et al. 1999). The lattice parameters (Ip) at 180 K are o = 7.I5 0.01 A, b = 4.527 0.008 A, c = 5.471 0.008 A.

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