Vibrations of the cubane molecule: inelastic neutron scattering study and theory

Cubane (C8H8) is an immensely strained molecule whose C–C–C bond angle is 90° rather than 109.5° as expected for sp3 bonding of carbon. We have measured the intramolecular vibrational spectrum of cubane using inelastic neutron scattering. The neutron data are used to test the transferability of various phenomenological potentials and tight-binding models to this highly strained molecule. Unlike these models, first-principles calculations of the INS spectrum (both energy and intensity) agree well with the experimental data.