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Table 1 Overview of the most important interactions occurring between two c losed-shell electron density distributions (R is the distance between the two centers of masses)

From: Charge density analysis for crystal engineering

Interaction type Origin Range Directionality Contribution
Electrostatic Coulomb attraction/repulsion between unperturbed electron densities Long range especially monopolar charges of ions (÷1/RL+1; where L is the sum of the multipole orders; L = 0 for charge-charge interactions) Monopole-monopole interactions are not directional; increasing directionality for higher multipolar moments Stabilization or destabilization, depending on the sign and orientation of the electrostatic moments of the interacting systems
Induced polarization Coulomb attraction between electron density of one molecule and field induced polarization of the other Shorter range (÷1/R4) Medium-Small Stabilization
Dispersion Coulomb attraction between mutually polarized electron densities Quite short range (÷1/R6) Small Stabilization
Short range repulsion The reduced probability of having two electrons with the same spin very close to each other (Fermi-hole) Very short range (÷1/R12 or exponential) None Destabilization
Charge Transfer Interaction between frontier orbitals of the interacting systems it implies partial covalence Occurs only for contacts shorter than van der Waals distances Very high Stabilization