Atomic definition

Filimonov DA, Poroikov VV, Borodina Y, Gloriozova T. Chemical similarity assessment through multilevel neighborhoods of atoms definition and comparison with the other descriptors. J Chem Inf Comput Sci 1999 39 666-70. 

CO adsorbed Pd/Al Oj, 37 69-70 diffuse reflectance spectroscopy, 34 14 Fowler-Nordheim equation, 21 72 Fraction exposed, of total metal atoms definition, 36 72-73... 

Filimonov, D., Poroikov, V., Borodina, Y. and Gloriozova, T. (1999). Chemical Similarity Assessment Through Multilevel Neighborhoods of Atoms Definition and Comparison with Other Descriptors. J.Chem.lnf.Comput.Sci.,39,666-670. 

During this time the question was raised whether a crystal of Si could be used as an atomic definition of the kilogram. Therefore a measurement of the mass of this atom was made using singly charged silicon ions and and ions as mass references [6]. Though we reached a statistical uncertainty of 10 we had to face the large q/A asymmetry which resulted in a systematic uncertainty of 10 . ... 

So far, we have reviewed how to derive an atomic decomposition of (S ) for a general a. However, the conditions (i) to (iv) are not sufficient to obtain a unique partitioning as they are all satisfied for arbitrary values of a, and hence additional conditions need to be defined in order to fix the parameter a. Ramos-Cordoba et al. investigated the behavior of the general formula of Eq. (8.25) with respect to a for a one-electron and a simple two-electron model system and concluded that the best choice of a should be 3/4. Furthermore, they demonstrated that the local spin values for diamagnetic molecules are very small indeed and similar if o = 3/4, independent of the basis set or atomic definitions, that is, the choice of the weighting functions physical-space analysis. Yet, a large... 

The free atom definition both scales were built up for isolated atoms. The electronegativity as energy per electron the given values are expressed in electron-volts. 

Cluster model scheme and periodical method were used in the molecular model calculations of active sites of zeolite catalysts results of both approaches are presented and discussed in this review. In cluster models of zeolite structures hydrogen boundary atoms (H ) were used to saturate dangling bonds of the Si and Al atoms. Definite restrictions were imposed on the optimization of positions of these boundary H atoms. In the optimization, the geometry of an appropriate fragment of zeolite lattice was taken from the experimental X-ray diffraction data [7]. Only Si-H and Al-H bond distances were optimized, while the positions of other atoms (except M), as well as directions of 0-H bonds, were kept frozen. The M ion was allowed to move freely in the structure. 

It is arbitrary how the electron density arising from basis functions located on different atoms is divided. The Mulliken procedure can give unphysical charges and shows a strong basis set dependence. Because of these shortcomings an atom definition which does not depend on the basis set is desirable. 

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