ELASTIC-NEUTRON-SCATTERING AND INELASTIC-NEUTRON-SCATTERING STUDY OF TETRATHIAFULVALENIUM-TETRACYANOQUINODIMETHANIDE (TTF-TCNQ) - NEW RESULTS

Several additional studies of tetrathiafulvalenium- tetracyanoquinodimethanide by elastic and inelastic neutron scattering have been performed. The temperature dependence of the lattice parameters b and asin were measured and no anomaly was observed at any of the transition temperatures, T1=54 K, T2=48.5 K, or T3=38 K. The 2kF satellites in the (h k 0) zone have been extensively studied. The temperature dependence of their intensity, position along a*, and the linewidth along a* are reported. In contrast with the earlier studies on the 2kF satellites possessing a c* component, the linewidths of the (h k 0) satellites increase to above 38 K and the satellites are undetectable above 48 K. The 4kF anomaly is shown not to arise from an anomaly in the longitudinal acoustic branch propagating along b, the chain direction. The possibility of the 4kF anomaly arising from an optical mode or being totally elastic above 54 K cannot be ruled out. The acoustic phonon branches for q propagating along the a* and c* directions have been measured and the corresponding elastic constants deduced. © 1979 The American Physical Society.