σ/σ- And π/π-interactions are equally important: multilayered graphanes.

Area of Science:

• Computational Chemistry
• Materials Science
• Condensed Matter Physics

Background:

• Graphanes and graphenes are 2D carbon allotropes with unique electronic and structural properties.
• Understanding their behavior in single-sheet, double-layered (diamondoids), and multilayered van der Waals (vdW) complexes is crucial for materials design.

Purpose of the Study:

• To investigate the structural and electronic properties of [n]graphanes, diamondoids, and multilayered [n]graphanes.
• To compare these properties with their parent [n]graphene systems.
• To analyze the influence of system size and layering on association energies and electronic band gaps.

Main Methods:

• Dispersion-corrected density functional theory (DFT) calculations using B97D/6-31G(d,p).
• Comparative calculations using M06-2X/6-31G(d,p), B3LYP-D3/6-31G(d,p), and SCS-MP2/cc-pVDZ single-point energies.
• System sizes studied ranged from n = 10 to 97 for graphanes and n = 10 to 130 for graphenes.

Main Results:

• Van der Waals complexes of graphanes exhibit significant association energies, reaching 120 kcal mol⁻¹ for a [97]graphane dimer.
• Graphanes display quantum confinement effects, with HOMO-LUMO gaps decreasing from 8.2 eV ([10]graphane) to 5.7 eV ([97]graphane), approaching the bulk value.
• Both graphanes and graphenes show decreasing band gaps with increasing system size, with graphene dimers approaching 2D metallic properties.

Conclusions:

• Layered graphane structures are energetically favorable and exhibit electronic properties that converge with system size.
• The electronic properties of layered graphanes and diamondoids become similar at particle sizes of 1 nm.
• The study provides insights into the size-dependent electronic and structural characteristics of graphane and graphene systems.