Ground-state degeneracy and slip energy in fractional-valency donor-acceptor molecular crystals

Slip energies have been calculated as the differences of the Madelung energies for Wigner lattices with identical values for the ionic valences for highly conducting TTF-TCNQ and NMP-TCNQ donor-acceptor molecular crystals in the region of the observed ionic valences. It is found that these energies are small, i.e., there are degenerate Wigner structures, which allow the occurrence of specific electronic excitations (kinks) responsible for the high electronic conductivities of molecular crystals with fractional valences.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 22, No. 4, pp. 464–469, July–August, 1986.