Poly-dodecahedrane: A new allotrope of carbon

Carbon is the most important chemical element and the theoretical study of its new allotropes can be of great interest. In this study, regular dodecahedron (dodecahedrane) oligomers (n = 1, 3, 5, 7, 9, 11, 13) by extending the dodecahedrane units in 3-dimensions were designed. Then, a theoretical study was conducted on their structures and electronic properties as potential new carbon allotrope. The cohesive energy (Ecoh) and $\Delta$G, were calculated. Experimental observations indicate that the Ecoh rises as the number of dodecahedrane units increases, whereas the Gibbs free energy change $\Delta$G decreases with an increase in the number of dodecahedrane units. The HOMO-LUMO energy gap (Eg) values, which represent electronic properties, decrease with increasing number of dodecahedrane units. Density functional theory (DFT) calculations of the novel carbon allotropes polydodecahedrane nanostructures have unveiled a previously unobserved symmetry, indicating intrinsic metallic behavior. The symmetrical distribution of partial charges was found in molecular electrostatic potential (MEP) diagrams for all oligomers, showing a tendency of the structures to maintain a symmetrical structural order as the number of monomer units increases. In addition, natural bond orbital (NBO) analysis of 13-units oligomer as largest designed structure reveals near-$sp^3$ hybridization for different carbons. Based on the calculated results, the structures have a tendency to extend in 3-dimensions and form a covalent network of poly-dodecahedrane with a unique structure consisting of interconnected cyclopentane rings. The results show that this exclusive configuration exhibits theoretical stability and suggests the potential for poly-dodecahedrane to be regarded as a novel carbon allotrope.