New polymorphic types of diamond

The results of calculations by PM3 and LDA-DFT methods of the structure and properties of six new polymorphic types of diamond, in which all atomic sites are crystallographically equivalent, are presented. The structures of LA5 (Cmca), LA7 (Cmcm), and LA8 (I4₁/amd) phases are obtained as a result of stitching graphene layers and of CA9 \((Fd\bar 3m)\) , CA10 \((R\bar 3m)\) , and CA11 (P6₃/mmc) phases by stitching fullerenelike clusters. For these phases the geometrically optimized structures are calculated and the structural parameters, density, sublimation energy, bulk modulus, electron density of states, and X-ray diffraction pattern are measured. It is found that the properties of polymorphic types of diamond depend on the degree of their structure deformation in comparison with the cubic diamond structure.