Numerical studies of ground state phase diagrams for the MMX chains

We study ground state phase diagrams for the MMX chains, using a one-dimens ional dimerized 3/4-filled extended Hubbard-Peierls model with sire diagona l and off-diagonal electron-lattice interactions. The ground states no obta ined mainly in the Hartree-Fock approximation, and their accuracy is checke d by the exact diagonalization of small clusters. We find a new phase in ad dition to Frequently considered phases and compare our results with experim ental results.