A Gravitational-Like Behavior of Dispersion Interactions
Sason Shaik
Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem 9190401, Israël
Wednesday 4 June 2025, 2:00pm CEST (Paris)
https://cnrs.zoom.us/j/94406006242?pwd=lkOchLa6X3PotLknH9rA1AW72FE3BN.1
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We present computational results for many-body dispersion (MBD) interactions in 42 pairs of molecules (hydrocarbons, silanes, corresponding fluorinated derivatives, pairs of CnHn cages, pairs which have multiple H---H contacts between the molecules, as well as pairs having π–π interactions), and pairs of Noble gas atoms. The results reveal that the MBD stabilization energy (EDISP,MBD) obeys a global relationship, which is gravitational-like.1 It is proportional to the product of the masses of the two molecules (M1*M2) and inversely proportional to the corresponding distances between the molecular centers-of-mass (RCOM,COM). This relationship reflects the interactions of instantaneous dipoles, which are generated by the ensemble of bonds/atoms in the interacting molecules and atoms. Using Grimme's D4-corrected dispersion energy (EDISP,D4), we find that the data sets for EDISP,MBD and EDISP,D4 are strongly correlated (R2=0.997). Based on valence-bond modeling, the molecular dispersion interactions occur primarily due to the increased contributions of the oscillating-ionic VB structures which maintain favorable electrostatic interactions; the. [RC+:H-+H :C-R] and [RC:-+H -H:C+R] structures; R symbolizes a general residue. The local charges (on the C and H atoms) are propagated to the entire ensemble of bonds/atoms in the R residues, thus bringing about the gravitational dependence of dispersion. The EDISP,MBD values for Noble-gas dimers are weak because the dispersion arises by mixing of excited states of the atoms (e.g., ns2np5(n+1)s1) into the ground states, ns2np6 shells via charge transfer and local excitations. These values are small.
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References :
[1] D. Danovich, A. Tkachencko, S. Alvrez and S. Shaik, J. Am. Chem. Soc. 2024, 146, 31198-31024.