Figure 1

Relaxed structures of lower diamondoids, identified experimentally in Ref. 5. Hydrogen atoms, terminating the carbon skeleton, are omitted from the diagrams for clarity. (a) The smallest diamondoid, adamantane, consisting of a single diamond cage. (b) Diamantane with two diamond cages. (c) Tetramantane with four diamond cages. (d) Decamantane with ten diamond cages.Reuse & Permissions

Figure 2

(Color online) Electronic structure of an (a) adamantane, (b) diamantane, (c) tetramantane, and (d) decamantane, depicted in Fig. 1. $E=0$ corresponds to the Fermi level. The fundamental band gaps are indicated in eV.Reuse & Permissions

Figure 3

Electronic, structural, and cohesive properties of diamondoid isomers considered here as a function of the polymantane order, reflecting the number of adamantane cages. (a) HOMO-LUMO gaps in the density of states (DOS). (b) C-C bond lengths, with the error bar reflecting the spread of the values within each system. (c) Formation energy per carbon atom $\Delta E∕n$ of the ${\mathrm{C}}_n{\mathrm{H}}_m$ diamondoids.Reuse & Permissions

Figure 4

(Color online) Comparison between structural and electronic properties of an elongated hexamantane isomer (left panels) and an infinite diamondoid chain (right panels). The equilibrium structure is shown in (a) and (d), with the large spheres denoting carbon and the small spheres hydrogen atoms. The electronic density of states is presented in (b) and (e), with the Fermi level at $E=0$. The one-dimensional band structure of the infinite diamondoid chain is shown in (f). The charge-distribution of electrons in the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of hexamantane is shown in (c). The corresponding charge distribution in the top valence and bottom conduction band of the diamondoid chain is shown in (g).Reuse & Permissions

Figure 5

(Color online) Structure, interaction energy, and electronic properties of unmodified and functionalized diamantanes. (a) Structural arrangement and (b) interaction energy of two unmodified diamantanes ${\mathrm{C}}_{14}{\mathrm{H}}_{20}$, separated by distance $d$. (c) Structural arrangement and (d) interaction energy of two chemically functionalized diamantanes ${\mathrm{C}}_{13}{\text{BH}}_{19}$ and ${\mathrm{C}}_{13}{\text{NH}}_{19}$, with the B and N sites in the neighboring molecules facing each other. (e) Equilibrium structure and (f) density of states of ${\mathrm{C}}_{13}{\text{BH}}_{19}$. (g) Equilibrium structure and (h) density of states of ${\mathrm{C}}_{13}{\text{NH}}_{19}$. The dashed lines indicate the position of the HOMO and LUMO in the unmodified diamantane, shown in Fig. 2b. Boron (light shading) and nitrogen (dark shading) sites are emphasized in (c), (e), and (g).Reuse & Permissions

Figure 6

(Color online) Total charge distribution in (a) ${\mathrm{C}}_{13}{\text{BH}}_{19}$ and (b) ${\mathrm{C}}_{13}{\text{NH}}_{19}$ in their equilibrium structure, shown in Figs. 5e, 5g. (c) Total charge distribution and (d) electronic density of states of ${\mathrm{C}}_{13}{\text{BH}}_{19}$ interacting with ${\mathrm{C}}_{13}{\text{NH}}_{19}$ in the structural arrangement depicted in Fig. 5c.Reuse & Permissions

Figure 7

(Color online.) Energetics of a diamantane molecule entering $\left(n,n\right)$ carbon nanotubes with various diameters. The end-on and side views of the insertion geometry are depicted in the left panels. The axial separation between the closest end of the diamantane and the nanotube is denoted by $z$, with $z<0$ corresponding to the diamantane outside and $z>0$ to the diamantane inside the carbon nanotube.Reuse & Permissions

Figure 8

(Color online) Energetics of diamantane, enclosed inside a $\left(6,6\right)$, $\left(7,7\right)$, and $\left(8,8\right)$ carbon nanotube, as a function of an off-axis displacement $y$. The geometry in end-on view is shown in the left panels.Reuse & Permissions