Neutron diffraction study of the compressibility of TIF-TCNQ under hydrostatic pressure

The linear axial compressibilities of a deuterated sample of TTF-TCNQ (tetrathiafulvalene-tetracyanoquinodimethane) have been measured by a neutron diffraction technique under hydrostatic pressures up to approximately 20 kbar at room temperature. The observed compressibilities along the crystallographic axes are, respectively, ksub(a)=2.7, ksub(b)=4.7 and ksub(c)=3.2 x 10-12cm2/dyne. These results indicate a strong Coulomb type interchain interaction. It is suggested that the dominant part of the crystal cohesion results from a stacking of strongly dynamically polarized TTF and TCNQ molecules acting as effective molecular dipoles