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Locally regular cluster

This chapter is the introduction to the physics of polycluster amorphous solids. At first the polycluster model was developed as a constructive foundation to describe some properties of metallic glasses. The assumption about the presence of a comparatively perfect local order (LO) (not necessarily of one type) leads naturally to the definition of the locally regular cluster (LRC), after which one must make only one step (not quite ambiguous) to introduce the definition of the polycluster structure. From this definition, there evolves the description of structure defects (Sect. 6.4). [Pg.209]

All other homoatomic Pn cluster anions are cage molecules with localized two-center-two-electron bonds. The cyclic [PnJ anion has been characterized by NMR spectroscopy for Pn = P [210], and structures are known for Pn = P, As, Sb, Bi (Table 2). A planar [Ps] anion has only been detected in solution by P NMR spectroscopy [210]. Envelop-shaped five- and six-membered rings are found for [Pns] and [Pe]", whereas [Asg]" deviates only slightly from planarity and has a chair conformation. The aromaticity of the planar anions [P4] and [Pe]" is distinct from that of regular 671-aromatic hydrocarbons and has been described... [Pg.100]

In 1962 Mackay introduced some amazing structures built with hard spheres as possible models for atomic clusters. Their external shape was that of a regular IC, and their size could be extended from the atomic scale to infinity. Despite the perfect fivefold symmetry of these structures, their internal local order was nearly that of a crystal. [Pg.56]

Due to its intrinsic complexity arising from the orbital multiplicity, the researches in this field have been almost exclusively concerned with the JT effect in rather simple systems like molecules, small clusters, and a single JT impurity center in solids in which itinerant electrons do not play an important role [2,3]. Even if the JT crystals, in which an infinite number of such JT centers occupy regular positions in a lattice, are considered in the context of the cooperative JT effect, relevant electrons in the system have usually been assumed to be localized [4]. [Pg.841]

Finally, in this particular investigation, we look at the same distributions for the six-particle Lennard-Jones cluster, the first that has two geometrically different locally stable structures. The lower-energy structure is a regular... [Pg.14]

Figure 12. Local equilibrium and saddle structures of a four-atom Morse cluster, M4. The local equilibrium structures (regular tetrahedron) and the Hrst rank saddle structures (planar rhombus) have the energy —6.00s and —5.02s, respectively. cp1 cp2, and tp3 are the hyper-angles that specify each reaction channel. When tp2 = 3, (P and cp3 cannot be determined uniquely and only the summation cp3 + Figure 12. Local equilibrium and saddle structures of a four-atom Morse cluster, M4. The local equilibrium structures (regular tetrahedron) and the Hrst rank saddle structures (planar rhombus) have the energy —6.00s and —5.02s, respectively. cp1 cp2, and tp3 are the hyper-angles that specify each reaction channel. When tp2 = 3, (P and cp3 cannot be determined uniquely and only the summation cp3 + <p3 is meaningful due to the convention for Euler angles in Eq. (50). Hence, we set (p3 = 0 when tp2 = 0.
Here we describe the isomerization dynamics of the four-atom Morse cluster, M4, in terms of the PAHC. At the local equilibrium point of this cluster, which corresponds to a regular tetrahedron stmcture, the three gyration radii are exactly degenerate, a a2 123 = 4.24, reflecting that the system is in an isotropic... [Pg.118]


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See also in sourсe #XX -- [ Pg.219 , Pg.229 , Pg.230 , Pg.232 , Pg.237 ]




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