Mechanical Response of Pentadiamond: A DFT and Molecular Dynamics Study

Abstract

Pentadiamond is a recently proposed new carbon allotrope consisting of a network of pentagonal rings where both sp 2 and sp 3 hybridization are present.In this work we investigated the mechanical and electronic properties, as well as, the thermal stability of pentadiamond using DFT and fully atomistic reactive molecular dynamics (MD) simulations. We also investigated its properties beyond the elastic regime for three different deformation modes: compression, tensile and shear. The behavior of pentadiamond under compressive deformation showed strong fluctuations in the atomic positions which are responsible for the strain softening at strains beyond the linear regime, which characterizes the plastic flow. As we increase temperature, as expected, Young's modulus values decrease, but this variation (up to 300 K) is smaller than 10% (from 347.5 to 313.6 GPa), but the fracture strain is very sensitive, varying from ∼44% at 1K to ∼5% at 300K.

Mechanical properties of 3D-printed pentadiamond

“…The mechanical behavior of considering infinite crystals (cyclic boundary conditions) and finite systems is different. The use of crystals [27] suppresses the lateral deformations, as the structures are infinite. In our case for the comparison with the finite printed structures is more appropriate to use finite structures.…”

“…Another porous carbon material recently proposed was the so-called pentadiamond [27][28][29][30]. It consists of a pentagonal covalent network containing a mixing of sp 2 (black) and sp 3 (blue) hybridized carbon atoms, as shown in figure 1(a).…”