Amorphous atomic distance

On the other hand, for an amorphous insulator, Aph is determined by the scattering of phonons with defects and can be very small, even approaching atomic distances. 

System Crystalline Atoms NNNa Distance Amorphous Atoms CNb Distance... 

On the other hand, a diffuse interface possesses a significantly wider core that extends over a number of atomic distances. A diffuse crystalline/amorphous phase interface is shown in Fig. B.3. Similar structures exist in crystal/liquid interfaces [5]. 

Poggemann, et al. [43] managed to obtain high spatial resolution AMF pictures of a fresh fracture surface of the amorphous silica, like that shown in Fig. 5.10. Seen are 0-0 and Si-O atomic distances, the Si04 tetrahedra, rings of such tetrahedra, as... 

DBM extremely well suited for depth profile analysis. For amorphous samples the depth resolution obtained with this technique has been shown to be limited only by the atomic microroughness extending to 4 atomic distances or 1-1.5 mn, which develops as a consequence of the statistical sputter removal. A section of a bombarding crater obtained under such conditions is shown in Figure 5A. 

In fig. 120, the scattering profile of the crystallized sample is compared with the peak positions for several La-Ni and La-Al compounds (Matsubara et al. 1992). All of the compounds except LaaNi explain the experimental data, although a complete match between the compounds and the data is not obtained. Thus, at the present stage, decisive conclusions about the crystalline phase(s) in the crystallized sample cannot be drawn. However, it is plausible that the atomic structure of the crystallized sample may be close to that of these compounds. From a calculation of interatomic distances in La Ni3 and LaNi, it is predicted that the atomic distance is estimated by assuming La-Ni pairs. Identical coordination numbers are obtained for both RDFs in fig. 119, although the difference between the atomic distances in the two RDFs for the crystallized sample is much larger than that for the amorphous samples. This may result from an incorrect assumption concerning the crystalline phase(s) present. 

Amorphous carbon is a carbon material without long-range crystalline order. Short-range order exists, but with deviations of the inter-atomic distances and/or inter-bonding angles with respect to the graphite lattice as well as to the diamond lattice. 

The term amorphous carbon is restricted to the description o/carbon materials with localized TT-electrons as described by PW Anderson (Phys.Rev. 109,1492 (1958)). Deviations in the C-C distances >5 (i.e. Ax/Xq > 0.05, where Xq is the inter-atomic distance in the crystal lattice for the sp as well as for the sp configuration) occur in such materials, as well as deviations in the bond angles because of the presence of dangling bonds . 

Above description >/amorphous carbon is not applicable to carbon materials with two-dimensional structural elements present in all pyrolysis residues of carbon compounds as polyaromatic layers with a nearly ideal inter-atomic distance of a = 142 pm and an extension >1000pm. 

Unlike the solid state, the liquid state cannot be characterized by a static description. In a liquid, bonds break and refomi continuously as a fiinction of time. The quantum states in the liquid are similar to those in amorphous solids in the sense that the system is also disordered. The liquid state can be quantified only by considering some ensemble averaging and using statistical measures. For example, consider an elemental liquid. Just as for amorphous solids, one can ask what is the distribution of atoms at a given distance from a reference atom on average, i.e. the radial distribution function or the pair correlation function can also be defined for a liquid. In scattering experiments on liquids, a structure factor is measured. The radial distribution fiinction, g r), is related to the stnicture factor, S q), by... 

EXAFS is a nondestructive, element-specific spectroscopic technique with application to all elements from lithium to uranium. It is employed as a direct probe of the atomic environment of an X-ray absorbing element and provides chemical bonding information. Although EXAFS is primarily used to determine the local structure of bulk solids (e.g., crystalline and amorphous materials), solid surfaces, and interfaces, its use is not limited to the solid state. As a structural tool, EXAFS complements the familiar X-ray diffraction technique, which is applicable only to crystalline solids. EXAFS provides an atomic-scale perspective about the X-ray absorbing element in terms of the numbers, types, and interatomic distances of neighboring atoms. 

In disordered materials such as amorphous silicon, the mobility is so low that it would correspond to a mean free path lower than the distance between atomic sites, which is not physically pertinent. In a classical paper, Anderson [20 has shown that disorder in a solid may result in a localization of the states, in which case the one-electron wave function takes an exponential form... 

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