  Two-dimensional carbon allotropes have attracted much attention due to their
extraordinary optoelectronic and mechanical properties, which can be exploited
for energy conversion and storage applications. In this work, we use density
functional theory simulations and semi-empirical methods to investigate the
mechanical, thermoelectric, and excitonic properties of Tetrahexcarbon (also
known as Tetragraphene). This quasi-2D carbon allotrope exhibits a combination
of squared and hexagonal rings in a buckled shape. Our findings reveal that
tetragraphene is a semiconductor material with a direct electronic bandgap of
2.66 eV. Despite the direct nature of the electronic band structure, this
material has an indirect exciton ground state of 2.30 eV, which results in an
exciton binding energy of 0.36 eV. At ambient temperature, we obtain that the
lattice thermal conductivity for tetragraphene is approximately 118 W/mK.
Young's modulus and the shear modulus of tetragraphene are almost isotropic,
with maximum values of 286.0 N/m and 133.7 N/m, respectively, while exhibiting
a very low anisotropic Poisson ratio value of 0.09.
