Open-core atom

Among the three subcategories, boronate compounds seemed to be the most efficient in coordinating with anions and enhancing lithium ion stability, although the number of electron-withdrawing substituents in boronate is only two. The authors thus inferred that the ability of these anion receptors to capture an anion depends not only on the electron-deficiency of the core atom but perhaps also on the steric hindrance presented by these substituents on the core. With only two substituents, the core of the boronates is obviously more exposed and therefore more easily accessible for an anion. The higher ion conductivity achieved by boronate additive therefore comes from the better balance between the electron-deficiency and steric openness of this compound as... 

As we have seen previously (Chapter 5), the eigenfunction for a polyelec-tronic atom is antisymmetric with respect to the exchange of the coordinates of any two electrons, and can be expressed as a Slater determinant whose elements are the various occupied spin-orbitals (or a linear combination of Slater determinants, in the case of open-shell atoms). The same appfies to polyelectronic molecules, the atomic orbitals being replaced by the various occupied molecular orbitals associated with the a and /3 spin-functions spin molecular orbitals. Thus, for the molecules H2O, NH3 or CH4 having five doubly occupied m.o.s (one core s orbital and four valence m.o.s), we have... 

Both HF and DFT calculations can be performed. Supported DFT functionals include LDA, gradient-corrected, and hybrid functionals. Spin-restricted, unrestricted, and restricted open-shell calculations can be performed. The basis functions used by Crystal are Bloch functions formed from GTO atomic basis functions. Both all-electron and core potential basis sets can be used. 

Tin has fourteen electrons outside of its krypton-like core. These may occupy the nine orbitals in the following three most stable ways (atomic electrons are indicated by spin vectors, bonding electrons by dots, the metallic orbitals by open circles) ... 

Porphyrazines (pz), or tetraazaporphyrins, are compounds that can be viewed as porphyrin variants in which the meso carbon atoms are replaced with nitrogen atoms, as Fig. 1 shows (1). This difference intrinsically gives porphyrazines discrete physiochemical properties from the porphyrins. In addition, despite their similar molecular architecture, porphyrazines are prepared by an entirely different synthetic route than porphyrins—by template cyclization of maleonitrile derivatives, as in Fig. 2, where the open circle with the A in it represents the peripheral substituent of the pz—rather than by the condensation of pyrrole and aldehyde derivatives (1). The pz synthetic route allows for the preparation of macrocycles with chemical and physical properties not readily accessible to porphyrins. In particular, procedures have been developed for the synthesis of porphyrazines with S, N, or O heteroatom peripheral functionalization of the macrocycle core (2-11). It is difficult to impossible to attach the equivalent heteroatoms to the periphery of porphyrins (12). In addition, the preparation and purification of porphyrazines that bear two different kinds of substituents is readily achievable through the directed cocyclization of two different dinitriles, Fig. 3 (4, 5, 13). 

The geometry of the Fe4S3 core is composed of a (open base) trigonal pyramid of iron atoms with a triply bridging sulfur atom apically positioned above each face. 

For all results in this paper, spin-orbit coupling corrections have been added to open-shell calculations from a compendium given elsewhere I0) we note that this consistent treatment sometimes differs from the original methods employed by other workers, e.g., standard G3 calculations include spin-orbit contributions only for atoms. In the SAC and MCCM calculations presented here, core correlation energy and relativistic effects are not explicitly included but are implicit in the parameters (i.e., we use parameters called versions 2s and 3s in the notation of previous papers 11,16,18)). 

The accessibility of new techniques such as EXAFS brings researchers a powerful tool for unambiguous determination of the true core metallic framework of such systems. Thus, the relationship between the parent carbonyl precursor, the support and the final metal-supported particles has been studied at the structural atomic level in some cases. This can allow differentiation of the catalytic behavior of supported metal particles with bulk-like properties from that of supported metal clusters, opening the way to understanding the mechanism of metal-catalyzed reactions and extending the concept of sensitive or insensitive structure reactions from metal aggregates to clusters. 

The star bums its own ashes, and the ashes of its ashes, but iron will not bum and the nuclear fire goes out. Blue giants with collapsed cores open like flowers and scatter their swarms of winged atoms in the sky. The dying of their light is acknowledged with the cry of Supernova ... 

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