X-ray scattering of TSeF-TCNQ and HMTSeF-TCNQ

Abstract

Some results of a X-ray diffuse scattering investigation on the charge transfer compounds TSeF-TCNQ and HMTSeF-TCNQ are presented. In the metallic state the results show the formation of a 1-D distortion or a Kohn anomaly in the phonon spectrum. For TSeF-TCNIQ this is observed below T~238 K and corresponds to a periodicity of (3.15± 0.05) $\overrightarrow {\left| b \right|}$ along the chain axis. For HMFSeF-TCNQ the distortion was detected even at room temperature and has a period of(2.7± 0.1) $\overrightarrow {\left| c \right|}$. In both materials the distortion has both transverse components. In the insulating state of TSeF-TGVQ below 29 K the 1-D distortion on each stack are correlated to form a 3-D super-lattice.