Density between regions

This normalization implies that a population parameter equal to 1 corresponds to a population of one electron for the spherically symmetric function d00. The nonspherical functions (/ > 0) represent a shift of density between regions of opposite sign. They have both positive and negative lobes which integrate to equal but opposite numbers of electrons. For these functions, the normalization expression... 

Table 5.10. Electronic structure of the CO, cluster distribution of valence electron density between regions of the cluster as defined by a multiple scattering Xa calculation [electron density values are percentages i (C-0) = 1.240 A]"...

The region of high electron density between the doubly bonded carbon atoms gives alkenes an additional reactivity and in addition to burning and reacting with halogens, alkenes will add on other molecules for example ... 

Polarization functions are essential in strained ring eompounds beeause they provide the angular flexibility needed to direet the eleetron density into regions between bonded atoms. 

This expression indicates that there is a decreased probability (indicated by the term —2(/>A(/>B) of finding the electrons in the region between the two nuclei. In fact, there is a nodal plane between the positive and negative (with respect to algebraic sign) of the two regions of the molecular orbital. As a simple definition, we can describe a covalent bond as the increased probability of finding electrons between two nuclei or an increase in electron density between the two nuclei when compared to the probability or density that would exist simply because of the presence of two atoms. 

The modem definition from IUPAC says, A covalent bond is a region of relatively high electron density between nuclei which arises (at least partially) from sharing of electrons, and gives rise to an attractive force and characteristic inter-nuclear distance . 

There are two types of discontinuity surfaces contact surfaces and shock fronts. There is no flow between regions separated by a contact surface, while shock fronts are crossed by the flow. A contact surface moves with the fluid and separates two zones of different density and temperature, but the same pressure. The normal component of the flow velocity is the same on both sides of a contact discontinuity... 

Heterogeneity of n values is related to a number of factors, including end groups, differences in density between amorphous and crystalline regions, anisotropic behavior of crystalline portions, incorporation of additives, and the presence of voids. 

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