In this paper, coupled-cluster CCSD/aug-cc-pVTz and related quantum chemistry methods are employed to perform He-He bond length scan for helium dimer and to obtain the electron density differences and figures for all of the points in the variation process of the bond length; the nature and formation mechanism of van der Waals interaction are interpreted by contiguously changing graphics. When the distance between helium atoms becomes short, paired electron cloud collide. Due to Pauli repulsion, electron cloud balls deform, forming a certain degree of electron avoid- ance as well as electron sharing, and then the van der Waals force is formed due to the equilibrium between the attract- tion and repulsion. The whole process is vividly presented by the animation.
S. M. Cybulski, R. R. T0czyl0wski, S. M. Cybulski and R. R. T0czyl0wski. Groundstate potential energy curves for He2, Ne2, Ar2, He-Ne, He-Ar and Ne-Ar: A coupled-cluster study. Journal of Chemical Physics, 1999, 111(23): 10520-10528.
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The Gordon Research Group. The General Atomic and Molecular Electronic Structure System (GAMESS) is a general ab initio quantum chemistry package.
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T. Lu. Multiwfn: A multifunctional wavefunction analyzer. Jour- nal of Computational Chemistry, 2012, 33(5): 580-592.