Application of the Space Group to the Molecular Orbital Treatment of Crystalline Iodine

The physical model of two-dimensional p-electron delocalization proposed by Bersohn for crystalline iodine is examined. The principal features of the model are adopted, including the Hückel method for writing one-electron orbitals and the restriction to nearest nonbonded neighbor interactions. Crystal symmetry is exploited in defining the matrix integrals. The secular equation is solved exactly for characteristic points in the Brillouin zone for the space group C2vII, and an approximate analytical solution is obtained for the general point. The theory semiquantitatively accounts for the experimental results of nuclear quadrupole coupling, crystal energy, and conductivity.