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Electron density magnetic determination

In order to perform the calculation., of the conductivity shown here we first performed a calculation of the electronic structure of the material using first-principles techniques. The problem of many electrons interacting with each other was treated in a mean field approximation using the Local Spin Density Approximation (LSDA) which has been shown to be quite accurate for determining electronic densities and interatomic distances and forces. It is also known to reliably describe the magnetic structure of transition metal systems. [Pg.274]

Nuclear Magnetic Resonance Spectra. The CNMR spectra of quinoxaline and a dozen 5-substituted quinoxalines have been determined for comparison with those of corresponding naphthalene derivatives. Aspects of the H, and NMR spectra of quinoxaline and related heterocycles have been correlated with the 7i-electron densities of the system." In contrast with the... [Pg.94]

Electron spin resonance, nuclear magnetic resonance, and neutron diffraction methods allow a quantitative determination of the degree of covalence. The reasonance methods utilize the hyperfine interaction between the spin of the transferred electrons and the nuclear spin of the ligands (Stevens, 1953), whereas the neutron diffraction methods use the reduction of spin of the metallic ion as well as the expansion of the form factor [Hubbard and Marshall, 1965). The Mossbauer isomer shift which depends on the total electron density of the nucleus (Walker et al., 1961 Danon, 1966) can be used in the case of Fe. It will be particularly influenced by transfer to the empty 4 s orbitals, but transfer to 3 d orbitals will indirectly influence the 1 s, 2 s, and 3 s electron density at the nucleus. [Pg.38]

In an attempt to relate calculated results to experimental findings for monomeric, lignin model compounds, preliminary work has compared theoretically determined electron densities and chemical shifts reported from carbon-13 nuclear magnetic resonance spectroscopy (62). Although chemical shifts are a function of numerous factors, of which electron density is only one, both theoretical and empirical relationships of this nature have been explored for a variety of compound classes, and are reviewed by Ebra-heem and Webb (63), Martin et al. (64), Nelson and Williams (65), and Farnum (66). [Pg.275]

Part II deals, in six chapters, with the principles underlying the progressive stages in the elucidation of internal structure. Chapters VI and VII deal with the principles of structure determination by trial Chapter VIII with the use of physical properties (such as habit, cleavage, and optical, magnetic, pyro- and piezo-electric properties) as auxiliary evidence in structure determination. In Chapter IX are to be found several examples of the derivation of complete structures. Chapter X gives an introductory account of the use of direct and semi-direct methods based on the calculation of electron density distributions and vector distributions from X-ray diffraction data. [Pg.8]

The metallic nature of concentrated metal-ammonia solutions is usually called "well known." However, few detailed studies of this system have been aimed at correlating the properties of the solution with theories of the liquid metallic state. The role of the solvated electron in the metallic conduction processes is not yet established. Recent measurements of optical reflectivity and Hall coefficient provide direct determinations of electron density and mobility. Electronic properties of the solution, including electrical and thermal conductivities, Hall effect, thermoelectric power, and magnetic susceptibility, can be compared with recent models of the metallic state. [Pg.102]

As far as rel. (1) indicates, for one atomic species such as H, or one single precise frequency will be absorbed. However, the nuclei are shielded from an external magnetic field by their electron cloud. The electron density around each nucleus may vary from molecule to molecule [101], and this variation modifies the absorbed frequency as given by rel. (1). The difference in the absorbing frequency of a particular atom from a reference atom is called chemical shift. The result field Ho, which determines the resonance behavior of the nucleus, will be, therefore, different from the applied field Happi, and using a shielding parameter a t can be written ... [Pg.192]


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See also in sourсe #XX -- [ Pg.93 ]




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