Cyclo-Graphyne: A Highly Porous and Semimetallic 2D Carbon Allotrope with Dirac Cones

We present a comprehensive characterization of Cyclo-graphyne
(CGY),
an emerging 2D carbon allotrope with a porous structure of sp- and
sp2-hybridized carbon atoms. Using density functional theory,
we systematically investigate its structural, energetic, dynamical,
electronic, mechanical, optical, and vibrational properties. The calculated
cohesive and formation energies are both comparable to those of other
synthesized graphynes, confirming its energetic viability. Phonon
dispersion calculations confirm its dynamical stability, while ab
initio molecular dynamics simulations indicate thermal stability up
to at least 1000 K. Electronic structure calculations reveal that
CGY is a semimetal featuring two Dirac cones in its electronic structure.
Mechanically, this material is highly compliant and isotropic, exhibiting
a Young’s modulus an order of magnitude lower than that of
graphene. The optical spectrum reveals strong ultraviolet absorption
and infrared reflectivity with an isotropic response, while the vibrational
spectra show distinct Raman peaks and rich infrared activity. These
properties position CGY as a promising candidate for future applications
in areas such as gas capture and separation, flexible nanoelectronics,
and optoelectronics.