On the origin of the phase transition of α-(BEDT-TTF)2I3

Following the experimental indications that some kind of dimerization which does not change a unit cell is associated with the first order MI transition at 135K of the title material, we have calculated changes of the electronic states due to the dimerization modes, and the resultant energy gains. We found that degree of dimerization to stabilize the insulating state is very large to be realistic and that the energy gain is too small to account for the transition. Hence we conclude that there should be other important missing links associated with this transition.