Charge-density distribution molecule

Gatti, C., R. Bianchi, R. Destro, and F. Merati. 1992. Experimental v. Theoretical Topological Properties of Charge Density Distributions. An Application to the L-alanine Molecule Studied by X-ray Diffraction at 23 K. J. Mol. Struct. (Theochem) 255, 409—433. 

For the 6 mol % doped device the number of dopant molecules inside the doped volume can be calculated with the hypothesis of homogeneous distribution of the molecules. With 12 ts of the averaged lifetime of the excited state of complex 53 and the additional assumption of homogeneous distribution of excited molecules, the upper level of the effective distance between excited molecules as a function of the current density can be estimated. Thereby, the charge density distribution was admitted to half of the doped zone, which is a reasonable assumption as demonstrated by model calculations [ 127]. This effective distance is directly related to the current-dependent quantum efficiency r)( ) of the device. 

Theoretical chemistry is informed by the observation of charge density distributions in crystals and molecules, and these do not appear as sets of discrete points. Conventional wisdom implicates the time scale of diffraction experiments for building up, what appears to be diffuse charge densities, by the statistical accumulation of data points. However, not only does quantum theory deny the existence of electronic positions and paths, but until it has been shown experimentally that the data points appear sequentially, the statistical argument is no more persuasive than the wave-mechanical. 

Necessary data about spatial distributions of electron charge density inside molecules had been taken from calculations by using of standard molecular orbital... 

In the last few years, several workers have analyzed charge density distribution in molecular crystals with non-linear optical (NLO) properties [71-74]. The NLO response can, in principle, be explained by an anharmonic distortion of the electron density distribution due to the electric field of an applied optical pulse. The polarization P induced in a molecule is... 

A molecule contains a nuclear distribution and an electronic distribution there is nothing else in a molecule. The nuclear arrangement is fully reflected in the electronic density distribution, consequently, the electronic density and its changes are sufficient to derive all information on all molecular properties. Molecular bodies are the fuzzy bodies of electronic charge density distributions consequently, the shape and shape changes of these fuzzy bodies potentially describe all molecular properties. Modern computational methods of quantum chemistry provide practical means to describe molecular electron distributions, and sufficiently accurate quantum chemical representations of the fuzzy molecular bodies are of importance for many reasons. A detailed analysis and understanding of "static" molecular properties such as "equilibrium" structure, and the more important dynamic properties such as vibrations, conformational changes and chemical reactions are hardly possible without a description of the molecule itself that implies a description of molecular bodies. 

The radial charge density from the resonant orbital is displayed in fig. 15. and the number of radial nodes identify this as a 4p orbital and not the lowest 2p that one would have expected from the successful qualitative correlation of LUMOs with resonances in e-molecule scattering /18/. However, the accumulation of the radial charge density distribution at small r values is a strong reminder of the 2p type orbital density distribution /120/. This feature,... 

C. Gatti, R. Bianchi, R. Destro and F. Merati, Experimental vs theoretical topological properties of charge density distribution—an application to the L-alanine molecule studied by X-ray diffraction at 23K, THEOCHEM, J. Mol. Struc. 87, 409 33 (1992). 

The closed surfaces S, on which the requirement (6.179) is satisfied, allow us to divide a molecule being present on the path of the reaction, into atoms. We say that a catastrophe took place if there occurs a qualitative change in the charge density distribution p and in its gradient Vrp on crossing by the control parameters R the critical position Rcr. Such a catastrophe is connected with a qualitative change in the division of a molecule being on the reaction path into atoms hence it reflects... 

None of these implementations can be used to study effects due to variar tion of the finite nucleus model, due to their limitation to a single finite nucleus model. Of course, it is unlikely that such variations lead to significant changes in the chemical behaviour of atoms and molecules, e.g., reaction enthalpies, valence electronic charge density distribution etc. However, the finer details of the electron distribution in the vicinity of heavy atomic nuclei will be more sensitive to the variation of the finite nucleus model, but this is clearly a field in the area of atomic and nuclear physics. 

D. Andrae, Finite nuclear charge density distributions in electronic structure calculations for atoms and molecules, Phys. Rep. 336 (2000) 413-525. 

---