Embedded ideal structure

At each magnification starting from low to high we observe more and more detailed information until atoms are observed. It is possible to describe a hierarchy of defects since they are embedded in the material - they are merely members of a set of discrete objects which represent deviations from the ideal structure. The analyst is faced with the task of describing the sets of defects and conditions under which they are detrimental to the operation of the device. 

Co-deposition describes the embedding of particles in a metal matrix during a plating process. The ideal structure of such materials is shown in Figure 12.1. Spherical particles of different sizes are embedded in a homogeneous metal matrix. Another form of particles is flakes. Co-deposition of mica flakes with Zn is shown as an example in Figure 12.2. 

To explain dendritic encapsulation, one needs to know something about dendrimer conformations and dynamics. These can be complex and difficult to map out. This problem leads to a chicken and egg conundrum (to crack a bad encapsulating joke). Ideally, one has information about structure that can be used to rationalize encapsulation behavior. However, as it is difficult to get structural (particularly conformational) information about dendrimers, structures are often proposed based on observed encapsulation behaviors. Thus, a central theme of this chapter will be that the redox unit, as it is perturbed by the structure of the dendrimer, acts as both embedded reporter and performer. This approach runs the risk of generating a circuitous argument. However, in combination with other methods of assessing structure, it hopefully can iterate to a self-consistent model. 

Figure 17 gives two examples of cluster film structure (a) clusters are embedded in matrix by co-deposition or, (b) isolated by a matrix via multilayering. The ability of the deposition technique to independently control these parameters makes it ideal for systematic studies of magnetic clusters. In this section, some recent work on FePt Ag and FePt C cluster films from our laboratory are reviewed. 

Switching from the very hydrophilic clays towards other inorganic nanoparticles, e.g., colloidal silica, leads, in the interplay with polymerization in miniemulsions, into a potential structural complexity, which covers the whole range from embedded particles (such as in the case of the calcium carbonate and carbon blacks) to surface bound inorganic layers (such as in the case of the clays). For basic research they are ideal systems to analyze complex structure formation processes in emulsions, since the original droplet shows a structure which is essentially established by molecular forces and local energy considerations, and which is ideally just solidified into a polymer structure. 

Since many experimental studies of 7-Fe were performed for 7-Fe particles in a Cu matrix (or Cu alloy, including Cu-Al) [113], [114], it is important to probe the electronic structure of the particle-matrix systems. Embedded-cluster methods are ideally taylored to treat small particles of a metal in a host matrix, a system that would require a very large supercell in band-structure calculations. DV calculations were performed for the 14-atom Fe particle in copper shown in Fig. 21 [118]. Spin-density contour maps were obtained to assess the polarization of the Cu matrix by the coherent magnetic 7-Fe particle. Examples are given in Figs. 22 and 23 for a Fe particle in Cu and 7-Fe in Cu with two substitutional Al. If the matrix is a Cu-Al alloy, this element is known to penetrate the Fe particle [114]. 

The ideal Costa scheme (ICS) is not practical due to the involved huge random codebook. Therefore, several suboptimal implementations of ICS have been proposed since 1999. A natural simplification of ICS is the usage of a structured codebook ULx, which in the most simple case can be constructed by a concatenation of scalar uniform quantizers. This approach, constrained to a sample-wise (scalar) embedding and extraction rule, is denoted in this article as scalar Costa scheme (SCS). The accurate and complete performance analysis of SCS is the main topic of this paper. 

The host data vector Xj resembles the data of the structure Mj to be modified by the watennarking mechanism. Ideally, all elements of Xj are independent, such that watermarking one element does not affect the other ones. Further, it should be impossible for an attacker to derive the unwatennarked data Xj from the watennarked data Sj. In the current version of our watennarking scheme, the host data contains the coordinates of all atoms. They are scaled such that a watennark of variance = 1 can be embedded without rendering the watennarked stmcture useless (see Section 5.4). 

The surfaces sketched above for the three-electron problem represent an ideal case. In a real situation, the minima of the states are embedded in the full space of coordinates and may be local minima or saddle points. Depending on the chemistry of the problem, there may also be barrierless paths from the ideal minima to other structures, and in these cases it is not possible to localize the structures in Figure 2.7 computationally. This problem is discussed in more detail in Section 2.5. 

When an adsorbate, such as CO, NO or H, is introduced to the hexagonally reconstructed surface, referred to henceforth as Pt 100 -hex, the reconstruction is lifted and the top layer Pt atoms adopt the ideal (1x1) structure. The formation of a chemical bond between top layer Pt atoms and the adsorbate increases the local embedding charge density experienced by the surface Pt atoms, the hexagonal top layer now experiences too large a charge density, and the (1x1)... 

Figure 5.1 Chemical embedding of active molecules in an ideal validation database. A distribution ofstructurallydiverse active compounds (gray) among inactive molecules (black) structurally related to actives but distant to other inactive compounds avoids artificial enrichments in model validation.

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