Addressing the Origin and Nature of Be–Ng (Ng = Noble Gas) Interactions among the Neutral Complexes with Be₂C

Density Functional Theory (DFT)-based calculations are performed to address the bonding interactions of noble gases (Ng═He-Kr) with the Be center in the neutral molecule Be₂C resulting in the formation of two types of complexes, Be═C═Be-Ng and Ng-Be═C═Be-Ng. The complexes are found to be increasingly stable with the increasing size of Ng atoms. The complexes with Ne stand out as an exception showing the minimum stability. This is corroborated from the delocalization indices, bond orders at the Be-Ng linkages, and chemical hardness parameters. The nature of the Be-Ng interactions is assessed from the topological parameters, which reveal a predominantly closed-shell interaction. This is consistent with an electron transfer interaction from Ng to the Be center. This electron transfer typically increases with the increasing size of Ng atoms with Ne being an exception. In quest of the nature of Be-Ng interactions, the Laplacian of electron density is assayed in combination with ELF and LOL analyses. Energy decomposition analysis reveals that the complexes are mostly sterically stabilized with destabilizing contributions from Pauli repulsion. The nature of the contribution of the exchange-correlation energy term is seen to depend on the method employed. The present results may add to the debate surrounding the position of He in the Periodic Table.