The thermodynamic properties were calculated from the phonon frequencies using the statistical thermodynamic expressions on a high precision sampling mesh in the Brillouin zone . For all three allotropes, C 4 , C 9 and C 12 , the temperature dependencies of the heat capacity at constant volume (C V ) are shown in Fig. in comparison with experimental values for diamond . The curves corresponding to the temperature change of the entropy S are also shown. The nearly linear increase in entropy with temperature is expected as a signature of increased disorder within the lattice. The C V = f(T) curve of C 4 in Fig. exactly follows the evolution of the diamond experimental points, but a relatively small deviation in magnitude can be observed for the calculated C V = f(T) curves of C 9 and C 12 . However, a better agreement with the diamond experimental points can be observed for C 12 . It can be proposed that although the novel allotropes are structurally different from diamond, especially with respect to the stacking of tetrahedra, they remain close to it dynamically and thermally.