The solid state of free radicals of bis(9-cyclohexylimino-1-oxyphenalenyl) boron is one of few neutral molecular systems which exhibit high conductivity at room temperature. The system is crystalline but highly anistotropic. We have performed band structure calculations based on the density functional theory on this system. It is evident from these studies that the system is quasi-one-dimensional with strong intermolecular interactions along one crystal direction. The bandwidth is $0.424\mathrm{eV}$ along this direction as compared to $0.055\mathrm{eV}$ perpendicular to it. Despite the quasi-one-dimensional character of the system, no signature of a Peierls distortion towards a dimerized state is observed. We argue that this is due to the fact that the Fermi energy lies slightly below the middle of the conduction band. In this case the electronic driving force for the distortion to occur is weakened and overcome by the restoring force of the lattice. Also the optical properties of the system have been investigated and the origin of the low lying excitations in the system has been clarified.

• Received 20 June 2006

DOI:https://doi.org/10.1103/PhysRevB.74.155111