Energetic stability, atomic and electronic structures of extended γ-graphyne: A density functional study

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Chemistry

Background:

• Graphene, a 2D material, has unique electronic properties but lacks a natural band gap.
• Graphyne and its derivatives (γ-GYs) offer tunable electronic structures by incorporating sp-hybridized carbon atoms.
• Understanding the energetic and electronic properties of γ-GYs with varying chain lengths is crucial for their application.

Purpose of the Study:

• To investigate the energetic stability and electronic structures of γ-graphyne and its derivatives (γ-GYs).
• To explore the influence of carbon chain length on the properties of γ-GYs.
• To determine the potential of γ-GYs as materials with tunable band gaps.

Main Methods:

• Density functional theory (DFT) calculations were employed.
• The energetic stability was assessed as a function of carbon chain length (n=0-22).
• Atomic and electronic structures were analyzed, focusing on the parity of carbon atoms in the chains.

Main Results:

• Even-numbered carbon chains (polyyne) are energetically more stable than odd-numbered chains (polycumulene).
• γ-GYs exhibit metallic behavior for odd n and semiconducting behavior for even n.
• Semiconducting γ-GYs possess a direct band gap of ~1.2 eV and low effective electron masses (0.1-0.2), independent of chain length.

Conclusions:

• Introducing sp carbon atoms into sp2-based graphene provides a novel route to engineer band gaps without doping or defects.
• γ-GYs with even-numbered chains offer a promising platform for electronic applications due to their tunable semiconducting properties and good charge transport characteristics.
• The parity of carbon atoms in the chains is a critical factor determining the electronic nature (metallic vs. semiconducting) of γ-GYs.