Graphene smaller amplitude and higher frequency. This phenomenon, named "membrane effect", was predicted by Lifshitz in 1952. A prediction that was published in 2015 suggested a melting point of ≈4125 K. Recent and more sophisticated modelling has increased this temperature to at least 5000 K. At 6000 K (the sun's surface having an effective temperature of 5,777 K) graphene melts into an agglomeration of loosely coupled doubled bonded chains, before becoming a gas. The carbon–carbon bond length in graphene is about 0.142 nanometers. Graphene sheets stack to form graphite with an interplanar spacing of . Graphene is the strongest material ever
Material properties of diamond Material properties of diamond Diamond is the allotrope of carbon in which the carbon atoms are arranged in the specific type of cubic lattice called diamond cubic. Diamond is an optically isotropic crystal that is transparent to opaque. Diamond is the hardest naturally occurring material known. Yet, due to important structural weaknesses, diamond's toughness is only fair to good. The precise tensile strength of diamond is unknown, however strength up to 60 GPa has been observed, and it could be as high as 90–225 GPa depending on the crystal orientation. The anisotropy of diamond hardness is carefully considered during diamond