We investigate the general applicability of the standard Peierls-Hubbard model, involving both on-site ($U$) and nearest-neighbor ($V$) Coulomb repulsions, by adding nearest-neighbor off-diagonal terms representing the bond ($W$) and mixed bond-site ($X$) electron-electron repulsive interactions. For a broad range of the site-diagonal Hubbard parameters ($U,V$), we find that the off-diagonal terms ($W,X$) initially enhance dimerization, thereby stabilizing the dimerized ground state.

• Received 11 May 1988

DOI:https://doi.org/10.1103/PhysRevB.38.12043