Superstructure peaks

FIGURE 2. (a) Out-of-plane and (b) in-plane XRD patterns of CajCoOi epitaxial films after annealing with Ca(OH)2 powder at each temperature (Fa = 25°C (as-prepared), 300°C, and 700°C) in air. Arrows indicate the superstructure peaks fl-om the Ca-ordered structures. 

Figure 7. Top The in-plane scattering intensities in reciprocal space at 0.275 V the locations of CTR s are shown by open circles crosses and the superstructure peaks by circles. Bottom Representation of the proposed structure in which the Pt atoms are shown by open circles and the Cu-Br overlayer atoms by filled circles. Insert Shows two scans through the (0, 0.741, 0.1) (left) and (1, 0, 0.1) (right) peaks, respectively.

Fig. 9. High-tempei-atme X-ray drf actiorr pattern of the Nd gBa, iCujO phase taken at 1000 C in air, which demonstrates orthorhombicity of this phase (multiple triplets) as well as the presence of superstructure peaks (107 and 117 as the brightest ones). The same is observed at room temperature and no orthorhombic-to-tetragonal transition exists for this Nd-rich phase. On the contrary, the oxygen- and Nd-poor NdBa2CujOT i phase, annealed at IOOO C, possesses a tetragonal symmetry of the lattice.

Fig. 76. (i) RHEED pattern of [1010] direction of an epitaxial Y (0001) film taken at 20 kV. (ii) The corresponding RHEED pattern of the sample films after deposition of 5 nm of Pd over layer at 300 °C. The superstructure peaks indicates an ordered Pd-Y alloy whereas the V form of the streaks indicate facetted surface, (iii) The RHEED pattern after depositing 0.5 nm (left pattern) and 5 nm of Pd at RT. The original Y reflexes are observed to vanish immediately after deposition of 0.5 nm of Pd and an amorphous/polycrystalline overlayer is formed (Borgschulte et al., 2001). 

Neutron diffraction patterns of annealed NbCx (0.81 S x S 0.88) (4,8) and TaCx (0.79 S X S 0.90) specimens display weak superstructure peaks along with intense structural lines, suggesting an incommensurate ordered phase with a composition close to M Cs (4). The parameter of the fee sublattice of metals for the ordered phase is larger than that for the disordered carbides, indicating that the volume of the crystal varies discontinuously during ordering (4). 

However, Stadler et al. argue that the intensity of the satelhte peaks which would be indicative of the superstructure is so low that they could not possibly be detected in X-ray measurements with the usual experimental resolution. Phases with intermediate tilt directions have been reported [16,17]. 

Another conductivity mechanism could be suggested for LB films of this polymer with Ag+ cations. Such cations can accept or release electrons easily, so in the layer of such cations the conductivity could be caused by electron transitions between the ions with different degrees of oxidation. With tunneling microscopy an anomaly in the dl/dV(V) curves near zero bias was discovered for the LB films in Ag form with an odd number of layers there was a conductivity peak some 150-200 mV wide (Figure 7.4, Curves 1, 3) but no anomaly for these same films with an even number of layers (Figure 7.4, Curve 2). For LB films with an odd number of layers the ordered superstructure of the scale 11.5 x 11.5 x lO cm has been found in a conductivity dl/dV (x,y) measurement regime. The scale of such a structure corresponds to 3 x 2 surface reconstruction (Figure 7.5). 

In the Equivalent Static Design Method, foundations are typically designed for the peak reactions obtained from the superstructure dynamic analysis. These reactions are treated as static loads, disregarding any time phase relationship. The basis for equivalent static design is discussed in 7M 5-856. 

Considerable evidence exits of the survival of Zintl ions in the liquid alloy. Neutron diffraction measurements [5], as well as molecular dynamics simulations [6, 7], give structure factors and radial distribution functions in agreement with the existence of a superstructure which has many features in common with a disordered network of tetrahedra. Resistivity plots against Pb concentration [8] show sharp maxima at 50% Pb in K-Pb, Rb-Pb and Cs-Pb. However, for Li-Pb and Na-Pb the maximum occurs at 20% Pb, and an additional shoulder appears at 50% Pb for Na-Pb. This means that Zintl ion formation is a well-established process in the K, Rb and Cs cases, whereas in the Li-Pb liquid alloy only Li4Pb units (octet complex) seem to be formed. The Na-Pb alloy is then a transition case, showing coexistence of Na4Pb clusters and (Pb4)4- ions and the predominance of each one of them near the appropiate stoichiometric composition. Measurements of other physical properties like density, specific heat, and thermodynamic stability show similar features (peaks) as a function of composition, and support also the change of stoichiometry from the octet complex to the Zintl clusters between Li-Pb and K-Pb [8]. 

Exposure of a clean Ni(l 11) to CO to form a c(4 X 2) CO superstructure yielded in the first linear scan in the negative direction a more pronounced peak b (solid line, panel B, Figure 31) compared to that in panel A in the figure, providing rather conclusive evidence that the feature in question is derived from the presence of CO on the surface. The potential at which this peak occurs is sufficiently negative for Li to UPD on Ni, as evidenced by the two sets of complementary peaks A,A and B,B shown more clearly in the second scan (dotted line) [54] hence, it seems reasonable to assume that the effect observed originates from interactions between coadsorbed UPD Li and CO on the surface. 

As seen in Figure 5.IB, the polymer forms a layered structure below the transition point, showing a well-developed system of SAXS peaks. Moreover, the ORD measurements (see Figure 5.2) exhibit drastic growth of the optic rotation in the IsoSm phase towards shorter wavelengths, in contrast to the proper isotropic melt of the same polymer above the transition point, suggesting some helix-like superstructural ordering in the mesophase with a pitch below 300 nm. That hypothesis was further supported with CD, dielectric spectroscopy, and UV-vis spectroscopy data. " Tlie critical importance of chirality for the formation of the IsoSm phase is also confirmed by... 

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