Coppens

An important conceptual, or even philosophical, difference between the orbital/wavefunction methods and the density functional methods is that, at least in principle, the density functional methods do not appeal to orbitals. In the former case the theoretical entities are completely unobservable whereas electron density invoked by density functional theories is a genuine observable. Experiments to observe electron densities have been routinely conducted since the development of X-ray and other diffraction techniques (Coppens, 2001).18... 

Tench and Coppens (Ref 13) photolyzed o-nitrobenzaldehyde, nitrobenzene, and nitroben-zoic acid with light > 3500A. ESR measurements revealed the presence of radicals for o-nitrobenzaldehyde (in solns and powder), with no radicals observed with nitrobenzene and... 

X-ray diffraction and the charge distribution in transition metal complexes. P. Coppens, Coord. Chem. Rev., 1985, 65, 285 (56). 

Coppen, A (1967) The biochemistry of affective disorders. Brit. J. Psychiatry 113 1237-1264. 

Tyrer, P (1979) Clinical use of monoamine oxidase inhibitors. In Psychopharmacology of Affective Disorders (Eds Paykel, ES and Coppen, A), Oxford University Press, Oxford, pp. 159-178. 

Inspection of Fig. 15.3 reveals that while for jo 0.1 nAcm , the effectiveness factor is expected to be close to 1, for a faster reaction with Jo 1 p,A cm , it will drop to about 0.2. This is the case of internal diffusion limitation, well known in heterogeneous catalysis, when the reagent concentration at the outer surface of the catalyst grains is equal to its volume concentration, but drops sharply inside the pores of the catalyst. In this context, it should be pointed out that when the pore size is decreased below about 50 nm, the predominant mechanism of mass transport is Knudsen diffusion [Malek and Coppens, 2003], with the diffusion coefficient being less than the Pick diffusion coefficient and dependent on the porosity and pore stmcture. Moreover, the discrete distribution of the catalytic particles in the CL may also affect the measured current owing to overlap of diffusion zones around closely positioned particles [Antoine et ah, 1998]. 

Malek K, Coppens MO. 2003. Knudsen self- and Fickian diffusion in rough nanoporous media. J Chem Phys 119 2801-2811. 

Hansen, N.K. and Coppens, P. (1978) Testing aspherical atoms refinements on small-molecule data... 

Papoular, R.J., Vekhter, Y. and Coppens, P. (1996) The two-channel maximum-entropy method applied to the charge density of a molecular crystal a-glycine, Acta Cryst., A52, 397 107. 

Coppens, P. and Hall, M.B. (Eds.) (1982) Electron Distribution and the Chemical Bond Plenum, New York and London. 

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