title: The Self-Association of Graphane Is Driven by London Dispersion and Enhanced Orbital Interactions.
abstract: We investigated the nature of the cohesive energy between graphane sheets via multiple CH···HC interactions, using density functional theory (DFT) including dispersion correction (Grimme's D3 approach) computations of [n]graphane σ dimers (n = 6-73). For comparison, we also evaluated the binding between graphene sheets that display prototypical π/π interactions. The results were analyzed using the block-localized wave function (BLW) method, which is a variant of ab initio valence bond (VB) theory. BLW interprets the intermolecular interactions in terms of frozen interaction energy (ΔE(F)) composed of electrostatic and Pauli repulsion interactions, polarization (ΔE(pol)), charge-transfer interaction (ΔE(CT)), and dispersion effects (ΔE(disp)). The BLW analysis reveals that the cohesive energy between graphane sheets is dominated by two stabilizing effects, namely intermolecular London dispersion and two-way charge transfer energy due to the σ(CH) → σ*(HC) interactions. The shift of the electron density around the nonpolar covalent C-H bonds involved in the intermolecular interaction decreases the C-H bond lengths uniformly by 0.001 Å. The ΔE(CT) term, which accounts for ∼15% of the total binding energy, results in the accumulation of electron density in the interface area between two layers. This accumulated electron density thus acts as an electronic "glue" for the graphane layers and constitutes an important driving force in the self-association and stability of graphane under ambient conditions. Similarly, the "double faced adhesive tape" style of charge transfer interactions was also observed among graphene sheets in which it accounts for ∼18% of the total binding energy. The binding energy between graphane sheets is additive and can be expressed as a sum of CH···HC interactions, or as a function of the number of C-H bonds.
authors.affiliation: Department of Chemistry, School of Science, China University of Petroleum (East China) , Changjianxi Road 66, 266580 Tsingtao, China.
authors.forename: Changwei
authors.initials: C
authors.lastname: Wang
authors.affiliation: Department of Chemistry, Western Michigan University , Kalamazoo, Michigan 49008, United States.
authors.forename: Yirong
authors.initials: Y
authors.lastname: Mo
authors.affiliation: Institute of Organic Chemistry, Justus-Liebig University , Heinrich-Buff-Ring 58, 35392 Giessen, Germany.
authors.forename: J Philipp
authors.initials: JP
authors.lastname: Wagner
authors.affiliation: Institute of Organic Chemistry, Justus-Liebig University , Heinrich-Buff-Ring 58, 35392 Giessen, Germany.
authors.forename: Peter R
authors.initials: PR
authors.lastname: Schreiner
authors.affiliation: Department of Inorganic and Physical Chemistry, Indian Institute of Science , Bangalore 560012 India.
authors.forename: Eluvathingal D
authors.initials: ED
authors.lastname: Jemmis
authors.affiliation: Institute of Chemistry and Lise Meitner Minerva Center for Computational Quantum Chemistry, The Hebrew University , Jerusalem 91904, Israel.
authors.forename: David
authors.initials: D
authors.lastname: Danovich
authors.affiliation: Institute of Chemistry and Lise Meitner Minerva Center for Computational Quantum Chemistry, The Hebrew University , Jerusalem 91904, Israel.
authors.forename: Sason
authors.initials: S
authors.lastname: Shaik