Cooling rate dependence of the lattice parameters of (TMTSF)2ClO4

We report a diffractometric determination of the thermal dependence of the triclinic lattice parameters of (TMTSF)2ClO4. Low temperature measurements show that c and γ differ significantly in the quenched (Q) and relaxed (R) states. Tight binding calculations of the band structure of the organic sublattice, neglecting the ClO4− potential, show that the variations of γ between the Q and R states do not affect appreciably the shape of the Fermi surface (FS). We thus propose that the nesting properties of the FS are destroyed below the anion ordering transition by the b∗/2 component of the ClO4− Coulomb potential.