Table 1.

Calculated properties of HCN (1, 2) and 1D pI chains 3–8

 Material ΔE*, kcal/mol Band gap, eV N=C–C=N dihedral angle, ° 1. HCN (g) 17.8 — — 2. HCN (s) 9.6 — — 3. pI threefold helix 1.7 4.5 110 4. pI fourfold helix 2.4 4.3 68 5. pI fivefold helix 4.5 3.8 39 6. pI sixfold helix 2.1 3.5 26 7. pI wave 0.0 2.2 ∼3† 8. pI planar 0.8 1.5 0
• * Energies per unit of HCN are from periodic HSE06 calculations, and are shown relative to the lowest energy structure 7.

• Average value for all N=C–C=N dihedral angles in the unit cell.