Gross atomic charge

The Prediction of Gross Atomic Charges and Bond Overlap Populations... 

In discussing gross atomic charges it must be realized that a given pattern of atomic charge densities in a molecule can be imposed by several factors. We identify three effects responsible for a molecular charge distribution ... 

C7-C3 1.3989 Barrier to inversion at sulfur 234 kJ mol-1 Gross atomic charges C5-C4-C3 carbon plane-S1 121.6 10.6... 

The calculation automatically gives a population analysis, yielding the following gross atomic charges for the four atoms ... 

Moving one electron to the a lone-pair orbital changes the polarity of the radical. The calculated gross atomic charges are now ... 

Here, Q- is the partial overlap population, namely, the electron population of the overlap region between the atomic orbitals y,- and Xj >n the MO atomic orbitals y,- and y, in the MO , and S,(, the overlap integral between atomic orbitals y,- and y . QH is the gross atomic population or the gross atomic charge on atom H and is given by the sum of the atomic orbital populations Qi. The net charge AQh is obtained from the difference between QH and the atomic number ZH, namely, the number of electrons in the neutral atom. 

In the early tests, total net positive and net negative overlap populations were considered separately, and the net positive -electron overlap populations were then the third term. No advantage was found in considering the small negative term separately and thus Equation 14 became the form used. The last term introduces some function of the polarity of the molecule, f(AX ). Approximate Coulomb energies were calculated for each molecule from the gross atomic charges, q. These were tried as a... 

We note that under the assumption of zero overlap, the atomic charges computed this way are the same as the standard Mulliken248,249 gross atomic charges.) Hence the differentiation of Equation [36] is straightforward, and, neglecting the dependence of on it delivers a new Fock matrix that includes the effects of polarization self-consistently, just as for the other quantum reaction field formalisms, namely,... 

Gradient Extremal (GE), 338 Gradient norm minimization, 333 Gradient of a function, 238 Greens function, 257 GROMOS force field, 40 Gross atomic charge, 218... 

R, E. Christoffersen and K. A. Baker, Chem. Phys. Lett., 8, 4 (1971). Electron Population Analysis. Gross Atomic Charges in Molecules. 

Notice that the shared electron density, is divided equally between the two atoms in question. The gross atomic charge on each atom is simply the sum of ah the belonging to that atom minus the nuclear charge of the atom on wliich orbital Xju is located. 

C) vs. the gross atomic charge on the C atoms (obtained from extended LCAO-MO calculations) in M(CH3)4 compounds [38]. 

Vibrational frequencies have been calculated using the 3-21G basis set and are tabulated in [1]. The gross atomic charges (6-31G ) are as follows. Boron a = 4.086, Ji = 0.356, total =... 

Gross atomic charge can be correlated with the electron binding energy chemical shift (normally Is binding energy) offers a fast method time scale 10. Difficulty arises in obtaining reproduceable spectra of ions in solid state (as salts). 

Notice that the shared electron density, P is divided equally between the two atoms in question. The gross atomic charge on each atom is simply the sum of all the q, belonging to that atom minus the nuclear charge of the atom on which orbital XfA. is located. This is called the Mulliken population analysis. The computed charge on an atom of a molecule is influenced by a number of factors such as the basis set chosen, the exact details of H , and whether electron correlation is taken into consideration or not. The Mulliken scheme is arbitrary in that it partitions the shared electron density equally between the two atoms. There are many other methods for population analysis, some perhaps preferable in that they do not appear to be as method and basis set dependent as the Mulliken scheme. 

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