In this paper, coupled-cluster CCSD/aug-cc-pVTz and related quantum chemistry methods are employed to calculate rare gas molecules and plot figures of electron density differences, the nature and formation mechanism of van der Waals interaction are interpreted graphically. We propose a quantum chemistry picture for van der Waals interac- tion: In the process of the collision of paired electron cloud of atoms or molecules, electron cloud balls deform due to Pauli repulsion effect, and a certain degree of electron avoidance as well as electron sharing are formed. The van der Waals force is the consequence of the equilibrium between the attraction and repulsion. We believe that the nature of van der Waals effect is acting of wavefunction, which results in the internuclear shared electron, so van der Waals ef- fect can also be seen as a kind of chemical force.
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