Tetramers clusters

Fig. 1.99. General schema for the trimerization reaction of ethylene to yield benzene in a final collisionally activated reaction step (CID). This reaction has been shown to proceed with W+ and U+ cations or the iron tetramer cluster Fe4+ as catalysts [480]...

Liao, D. W, Balasubramanian, K. (1992). Electronic structure of the III-V tetramer clusters and their positive ions. Journal of Chemical Physics, 96(12),... 

In the recent past, our group has explored the possibility of aromaticity in several tetramer clusters comprising of homo- and heteroatomic elements [136-138]. The... 

These tetramer clusters are similar to that of Al, where one of the Al atoms has been replaced by a group V element, thus leading to the formation of a neutral analog of the A1J cluster. The prime objective for the study of this series of clusters is to investigate how the molecular orbitals of the Alj" cluster and, in particular, how the... 

Total Energies, Interatomic Separations (A), Binding Energy (B.E.), Vertical Ionization Potentials (VIP), Vertical Electron Affinity (VEA), and Global Hardness i) for Tetramer Clusters... 

It is known that the aromatic molecules possess cyclic and planar structures having high chemical and structural stability. From our previous calculations it is clear that all investigated tetramer clusters have very high IP and low EA, which can be regarded as an important parameter to understand their electronic stability. Other than this, the structural stability of these clusters can be verified from their interactions with any reactive species. Benzene, which is universally accepted as a leading... 

Nigam, S. Majumder, C. Kulshreshtha, S. K., Structure and bonding of tetramer clusters theoretical understanding of the aromaticity, J. Mol. Struct. (THEOCHEM) 2005, 755,187. 

Copper clusters containing two to four atoms have been formed (94) in argon and methane, whereas large, colloidal-copper particles resulted in dodecane matrices (94). The authors suggested that the "birth of the band structure of copper is clearly visible on passing from the dimer to the tetramer, with CU4 already possessing many of the features of the bulk metal (94). 

The 8V+ 2 rule has been completely substantiated by the calculated ground state geometries of tetramers in Table 2 [7], The cluster (lOe) is linear [11]. The Si/" cluster (18e) has a butterfly structure (Dp [18],... 

The MoFe proteins are all a2 2 tetramers of 220-240 kDa, the a and (3 subunits being encoded by the nifD and K genes, respectively. The proteins can be described as dimers of a(3 dimers. They contain two unique metallosulfur clusters the MoFeTSg homocitrate, FeMo-cofactors (FeMoco), and the FesSy, P clusters. Neither of these two types of cluster has been observed elsewhere in biology, nor have they been synthesized chemically. Each molecule of fully active MoFe protein contains two of each type of cluster 2-7). 

If the reverse of Reaction 1 is slow compared to 2 ( the colli sional stabilization step) then overall cluster growth will not depend strongly upon the total helium pressure. This is found to be the case using RRK estimates for k n and hard sphere collision cross sections for ksn for all clusters larger than the tetramer. The absence of a dependence on the total pressure implies that the product of [M] and residence time should govern cluster growth. Therefore, a lower pressure can be compensated for by increasing the residence time (slower flow velocities). 

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