  We investigate ground state properties of a quasi-one-dimensional
electron-lattice coupled model for quarter-filled molecular conductors. The
effective one-dimensional extended Hubbard model coupled to adiabatic lattice
degree of freedom is derived by the inter-chain mean-field approximation and
solved by Lanczos exact diagonalization method. We find that the critical
behavior among lattice tetramerized states with different charge-lattice
ordered patterns is sensitively affected by the inter-chain Coulomb
interaction, lattice anharmonicity, and intrinsic dimerization. This indicates
a subtle balance between these states originating from strong correlation and
reduced dimensionality.
