Orientational phase transitions in quadrupolar strands with itinerant-electrons

We consider a linear strand of chemically equivalent molecules of spin S = 1 which are free to rotate about their centres of mass fixed to a rigid lattice. The molecules interact via nearest-neighbour quadrupolar interactions and the electrons, occupying a half-filled, tight-binding conduction band, hop between nearest-neighbour molecules only. With a mean-field theory, we study the dependence of the metal-insulator phase transition temperature T_c on the quadrupole-quadrupole interaction, the electron-quadrupole interaction as well as the bandwidth of the conduction band.