THERMAL-BEHAVIOR OF (TMTSF)(2)CLO4 LATTICE-PARAMETERS IN THE RANGE 10K-300K

We report a new investigation of the triclinic lattice thermal behaviour of (TMTSF)(2)ClO4 in order to elucidate the tricky interplay between the structural and electronic properties of this salt. The nature of the ground state depends strongly on the cooling rate of the sample in the vicinity of the ClO4 anion ordering transition occuring at 24K. In the range 100-300K, the thermal expansion is rather anisotropic: a,b and alpha show an expansion break near 170K also perceptible on the volume. Below 50K, all the parameters exhibit thermal anomalies. In addition, the lattice parameters of quenched and relaxed samples present quite different values below about 30K. This difference is particularly significant for the c and gamma parameters.