Tsai clusters

In the case of i-Cd-Yb, a solution has been found through the substitution of equal amounts of Ag and In for Cd, leading to a QC with stoichiometry Ag42ln42Ybij, which is isostructural to i-Cd-Yb. The building block of i-Cd-Yb is a 44-atom regular triacontahedron or Tsai-cluster [201]. The six-dimensional hyperlattice is P type or primitive, whereas the Al-based icosahedral QCs are described by a six-dimensional F type of face-centered hypercube. The surfaces of isostructural i-Ag-In-Yb thus differ in structure and chemistry from aU previously investigated QC surfaces. 

Tsai, C.J. Jordan, K.D., Use of the histogram and jump-walking methods for overcoming slow barrier crossing behavior in Monte Carlo simulations applications to the phase transitions in the (Ar)i3 and (FbOjs clusters, J. Chem. Phys. 1993, 99, 6957... 

So far, three types of i-QCs appear in the literature Mackay [17], Bergman [18], and Tsai types [19], which have been differentiated on the basis of the polyhedral cluster sequences observed in the respective 1/1 AC structures. These are commonly represented as shown in Fig. 2. An i-QC is concluded to be Mackay-type if its 1/1 AC contains a 54-atom multiply endohedral cluster ordered, from the center out, as a small icosahedron (12 atoms), a larger icosahedron (12), and an icosidodecahe-dron (30). This motif occurs in ACs that consist of transition metals and main-group elements on the right side of the periodic table such as Al-(Pd,Mn)-Si [17,20]. In... 

Fig. 2 Schematics of the multiply endohedral clusters in Mackay-, Bergman-, and Tsai-type 1/1 ACs...

Fig. 19 The linkages between neighboring triacontahedral clusters in the Tsai-type 1/1 ACs along a the twofold axes, and b the threefold axes. The 2/1 ACs exhibit same linkages although they have different atom identities and symmetries. All decoration atoms of the triacontahedra are omitted for clarity. (Adapted with permission from [83], Copyright 2006 American Chemical Society)...

All the active metals in Tsai-type clusters lie on and define only the icosahedral shell. As a result, the global percentages of the active metals in Tsai-type phases are always — 157/, in contrast to that in Bergman-type phases ( 32%, below). 

Bergman- and Tsai-type clusters have the same geometric types for the second, third, and fifth shells, with the innermost and the penultimate shells being different. Particularly, the third (icosahedral) shell and the outmost triacontahedral shell define comparably sized spheres for both, but the other three shells for Tsai types are about 1.0 A smaller in diameter than for Bergman types. 

Fig. 21 a Polyhedral view of the unit cell, and b of the environment of a triacontahedron in the Bergman-type Mg27AlnZn47 2/1 AC (Pa3) in terms of triacontahedral clusters and prolate rhom-bohedra. Notice that both results are similar to those shown in Fig. 20 for Tsai-type 2/1 ACs. (Adapted with permission from [91]. Copyright 2006 The National Academy of Science USA)... 

Recently, some models (e.g., Halpin-Tsai, Mori- Tanaka, lattice spring model, and FEM) have been applied to estimate the thermo-mechanical properties [247, 248], Young s modulus[249], and reinforcement efficiency [247] of PNCs and the dependence of the materials modulus on the individual filler parameters (e.g., aspect ratio, shape, orientation, clustering) and on the modulus ratio of filler to polymer matrix. 

Compared to other models (e.g., Voigt-Reuss, Halpin-Tsai, modified mixture law, and Cox), the dilute suspension of clusters model promulgated by Villoria and Miravete [255] could estimate the influence of the dispersion of nanofillers in nanocomposite Young s modulus with much improved theoretical-experimental correlation. 

Zhou TJ, Mo YR, Zhou ZH, Tsai K. Density functional study on dihydrogen activation at the H cluster in Fe-only hydrogenases. Inorg Chem. 2005 44(14) 4941-6. 

This surface science research was supported by the Division of Chemical Sciences, Office of Basic Energy Sciences, U. S. Department of Energy under contract No. W-7405-Eng.-48 and the cluster chemistry by the National Science Foundation. The nickel and platinum surface studies were done by Cynthia Friend and Min-Chi Tsai, respectively and the cluster chemistry by Dr. Mamoru Tachikawa. The molecular orbital studies are collaborative with... 

Tsai DP, Kovacs J, Wang Z, Moskovits M, Shalaev VM, Suh JS, Botet R (1994) Photon scanning tunneling microscopy images of optical excitations of fractal metal colloid clusters. Phys Rev Lett 72(26) 4149... 

S. Ramachandran, B.-L. Tsai, M. Blanco, H. Chen, Y. Tang, and W. A. Goddardlll, Atomistic Simulations of Oleic Imidazolines Bound to Ferric Clusters, J. Phys. Chem. A 101, 83-89 1997. 

A model system that is so simple that detailed studies can be performed is that of a cluster of identical atoms for which it is assumed that the total energy can be written as a sum of pair potentials, each one being a simple Lennard-Jones potential. This system was studied by Tsai and Gordon,8 who found a rapidly increasing number of inequivalent metastable structures as a function of size, cf. Table 1. In Figure 2 the results have been fitted with an exponential, a exp(bN), and it is seen that the fit follows the calculated results fairly close. The fit gave a = 0.00341 and b = 0.983, which in turn means that for N = 55 the fit predicts that of the order of 1021 inequivalent minima exist. 

Eigenmode Methods. - In the previous section we discussed the results of Tsai and Jordan8 on the number of metastable structures for clusters with... 

As the last example we shall study clusters of water molecules. Here, we have clusters formed by only weakly interacting units, but for which the units have an internal structure and, consequently, the interactions are directional. For water clusters the TIP potentials are very popular and have, therefore, been used in optimizing the structure of water clusters. One of the first studies in this direction is due to Tsai and Jordan8 who used their eigenmode method (see Section 2.4) in optimizing the structure for clusters with up to 5 units. Later... 

In their discussion of the eigenmode method, Tsai and Jordan8 illustrated the approach through two simple systems. One of those was Lennard-Jones clusters, and the other was small clusters of water molecules. For both they tried to identify as many local total-energy minima and saddle points as possible. The numbers for the Lennard-Jones clusters are reproduced in Table 1 and it is remarkable to see that the number of transition states exceeds by far the number of local total-energy minima. This was also the case for the clusters of water molecules. 

Lin, T.-H. and Tsai, K-C. (2003) Implementing the Fisher s discriminant ratio in fe-means clustering algorithm for feature selection and data set trimming. /. Chem. Inf. Comput. Sci., 44, 76-87. 

Kim et al. [2] were apparently the first to apply ab initio methods to (H20)e, carrying out SCF optimizations of the hexamer as early as 1988. However, as it became possible to carry out MP2 calculations with suitable flexible basis sets on water clusters, it became clear that inclusion of electron correlation effects is crucial for describing the bonding in these species [5,11,12,20,23,67,68]. The first MP2 level calculations on (H20)6 were by Tsai and Jordan [12]. Subsequently, Kim and coworkers [69,70], Xantheas et al. [71],... 

Tsai FT, Chiou SJ et al (2005) Dinitrosyl iron complexes (DNICs) [L2Fe(NO)2]- (L = Thiolate) interconversion among Fe (NO)2 DNICs, Fe(NO)2 DNICs, and [2Fe-2S] clusters, and the critical role of the thiolate ligands in regulating NO release of DNICs. Inorg Chem 44 5872-5881... 

Structure and Hormonal Regulation of the Ovalbumin Gene Cluster Bert W. O Malley, Savio L. C. Woo, and Ming-Jer Tsai... 

Figure 10.6 Kinetic study of the dissociation of H H20. (a) Decay of the cluster ions with increasing trapping time in a 22-pole ion trap operated at various temperatures and (b) the dissociation rate constant of cluster ions at various temperatures [43]. Reprinted with permission from Wang, Y.-S., Tsai, C.-H., Lee, Y.T., Chang, H.-C., Jiang, ].C., Asvany, O., Schlemmer, S., Cerlich, D. (2003) Investigations of Protonated and Deprotonated Water Clusters Using a Low-temperature 22-pole Ion Trap. j. Phys. Chem. A 107 4217-4225. Copyright (2003) American Chemical Society...

Wang Y-S, Tsai C-H, Lee YT, Chang H-C, Jiang JC, Asvany O, Schlemmer S, Gerlich D. (2003) Investigations of protonated and deprotonated water clusters using a low-temperature 22-pole ion trap. J. Phys. Chem. A 107 4217-4225. 

C. J. Tsai and K. D. Jordan, Use of an eigenmode method to locate the stationary points on the potential-energy surfaces of selected argon and water clusters. J. Phys. Chem. 97(43), 11227-... 

It should be mentioned that in general, hard phase clusters can be non-spherical, as discussed in various earlier papers. In this case, the modulus increase could strongly depend on the aspect ratio the effect of the aspect ratio can be modeled through the micromechanical models of Halpin and Tsai [55] or Mori and Tanaka [56]. However, as we already commented above, below the spherical-to-cylindrical transition, most of the hard phase nano-domains have an aspect ratio close to 1. Above the spherical-to-cylindiical transition that is in our model associated with percolation threshold, most of the cylinders participate in the formation of the percolated hard phase, while the soft phase primarily contains hard phase islands with smaller aspect ratios. Therefore, in our analysis we assume that all the fillers dispersed within the soft phase are spherical (or have aspect ratios close to one). 

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