Extended electron distribution charges

Similarly to ROCS, the Cresset FieldScreen approach [31, 32] considers multiple 3D conformations. These are generated with a force field based on nonatom-centered extended electron distribution charges (XED). From the interaction energy with molecular probes, four 3D field properties are then calculated steric, hydrophobic. 

The extended Electron Distribution (XED) force field was first described by Vinter [96]. This force field proposes a different electrostatic treatment of molecules to that found in classical molecular mechanics methods. In classical methods, charges are placed on atomic centers, whereas the XED force field explicitly represents electron anisotropy as an expansion of point charges around each atom. The author claims that it successfully reproduces experimental aromatic ji stacking. Later, others made similar observations [97]. This force field is now available in Cresset BioMoleculaf s software package [95]. Apaya et al. were the first to describe the applicability of electrostatic extrema values in drug design, on a set of PDE III inhibitors [98]. 

Although the quantum problem seems to be solved by the hydrodynamics of a continuous distribution of electricity with charge density proportional to mass density, this approach has never been accepted as a serious alternative, largely because of doubts raised by Madelung himself. The most important of these, concerns the self-interaction between the charge elements of an extended electron. 

Since LaH and LuH differ by the 4fshells, a comparison of the two molecules is in order. Pyykko shows the plot of the spherically averaged radial electron densities (fig. 30). As seen from fig. 30, the LuH 6s electron distribution is shifted to the left with a maximum occurring to the left of the corresponding maximum of LaH. This means that the 6s orbital of Lu is contracted since the 4f shells incompletely shield the nucleus but the nuclear charge is increased by 14 for Lu compared to La. This is the effect of the lanthanide contraction. However, the LuH 5d electron distribution is more extended... 

The sum over Q2 in c must extend beyond the sum over in such a way that all contributions to the electronic charge of the cell Qi are properly taken into acount. This is necessary, since the electron population of a given cell is built up according to equation (1.68) as a sum over a certain number of neighbors. If one would use the same radius (measured from the reference cell) for the lattice sums over Q2 and qi, the tail of the electron distribution belonging... 

---