Charge-density concentration and electron-electron coalescence density in atoms and molecules - art. no. 034502

Values for the average electron density [rho] and the electron-electron coa lescence density or intracule density at the origin I(0) have been calculat ed for a number of atoms and molecules using several ab initio methodologie s. [rho] can be taken as a measure of local one-electron density concentrat ion, and shows little dependence on the theoretical level employed. In cont rast, I(0) has found to be highly dependent on the level of calculation. In particular, for a given nb initio method, the difference [rho]/4-I(0) can be related to the degree of Coulomb electron correlation introduced by that method in an atomic or molecular system.