Stability, elastic properties and deformation behavior of graphene-based diamond-like phases

The stability, elastic moduli and deformation behavior of graphene-based diamond-like phases are examined by molecular dynamics simulations. Three important criteria are considered to study stability of the structure within applied methods. Molecular dynamics simulations are performed to derive stiffness and compliance coefficients, and stress-strain curves under hydrostatic compression of diamond-like phases. The analysis of elastic properties (Poisson's ratio, Young's modulus and shear modulus) is carried out. Analytical calculations are used. From the obtained stability criteria, it is found that only two graphene-based diamond-like phases, LA3 and LA6, instead of eight known, can be considered stable in molecular dynamics approach. Young's modulus, measured in linear elastic regime, of stable phases orientationally dependent: values in different directions can differ two times. Analysis of the variability of shear modulus showed that for LA6 values are much higher than for LA3. Again, shear modulus are orientation-dependent for some directions. In non-elastic regime, stable diamond-like phases can be stretched until 0.012 and compressed until 0.1. The main mechanisms of non-elastic deformation is stretching of the covalent bonds and valent angles.