Stacking of polycyclic aromatic hydrocarbons as prototype for graphene multilayers, studied using density functional...

Area of Science:

• Materials Science
• Computational Chemistry
• Condensed Matter Physics

Background:

• Interlayer pi-pi interactions are crucial for the properties of graphene and related carbon nanomaterials.
• Understanding these interactions requires accurate theoretical models that capture both short-range and long-range forces.

Purpose of the Study:

• To investigate the influence of finite size on interlayer pi-pi interactions in graphene models.
• To determine the impact of model size, stacking order, and layer number on binding energies and energy gaps.

Main Methods:

• Density Functional Theory (DFT) was employed to model interlayer pi-pi interactions.
• An empirical R(-6) term was incorporated to account for long-range dispersive interactions.
• The method was calibrated using benzene dimer configurations against existing computational data.

Main Results:

• Binding energies and energy gaps of polyaromatic hydrocarbon models (graphene analogs) were found to be highly sensitive to their finite size.
• Stacking order and the number of layers had a minimal effect on these properties.
• A broad variation in the energy gap (1.0–2.5 eV) was observed, primarily driven by changes in model size.

Conclusions:

• The size of finite graphene models significantly dictates interlayer pi-pi interactions and electronic properties.
• The observed broad energy gap variation highlights the potential for tunable visible-range luminescence in size-controlled carbon nanomaterials.
• These findings provide insights for designing carbon-based nanomaterials with specific optoelectronic functionalities.