  A quasi-2D semiconductor carbon allotrope called tetrahexcarbon, also named
tetragraphene, was recently proposed featuring an unusual structure combining
squared and hexagonal rings. Mechanical and electronic properties of
tetragraphene have been predicted based on first-principles Density Functional
Theory (DFT) calculations. However, a comprehensive study of its mechanical
behavior under different temperatures is still lacking. In this work, using
fully atomistic reactive molecular dynamics (MD) simulations, we investigate
the mechanical properties of monolayer tetragraphene under tensile strain from
the linear regime up to the complete structural failure (fracture). Different
temperatures were considered and the results were compared to that of two other
known planar carbon allotropes: graphene and penta-graphene. One interesting
result is that tetragraphene experiences a transition from crystalline to an
amorphous structure by either temperature or tension application. At room
temperature, the critical strains along the two orthogonal unit-cell directions
of tetragraphene are 38\% and 30\%, which is higher than that for graphene and
penta-graphene. Tetragraphene Young's modulus values along its directions are
from three to six times smaller than that of graphene and about 57\% that of
penta-graphene at room temperature. Ultimate tensile strength values along the
two directions of tetragraphene were obtained and also shown to be smaller than
that of graphene and penta-graphene.
