Entropic Evidence for Cooperation of Multiple Instabilities upon a Metal-Insulator Transition in (EDO-TTF)2PF6

Kazuya SAITO, Satoaki IKEUCHI, Akira OTA, Hideki YAMOCHI and Gunzi SAITO

The entropy of the peculiar metal-insulator transition of the title compound was measured and analyzed, resulting in the conclusions that the mechanism of this transition is the catastrophic cooperation of multiple instabilities: Peierls instability, charge order and anion ordering.
(Chem. Phys. Lett., 401, 76-79 (2004))

Calorimetric Study of Metal-Insulator Transition in (DIMET)2I3

Kazuya SAITO, Akane SATO, Koichi KIKUCHI, Hiroyuki NISHIKAWA, Isao IKEMOTO and Michio SORAI

Heat capacity of a quasi-one-dimensional organic conductor (DIMET)2I3 has been measured by chopped-light ac calorimetry below room temperature. An anomaly due to a metal-insulator transition has been clearly detected around 40 K. The magnitude of the anomaly is analyzed through comparison with other Q1D conductors. A possible SDW mechanism is suggested.
(J. Phys. Soc. Jpn., 69, 3602-3606 (2000))

Thermodynamic Metal-insulator Transition in a Hydrogen-Bonded Organic-Inorganic Hybrid Conductor, [Pd(H2-xedag)(Hedag)].TCNQ (x = 1/3)

Kazuya SAITO, Yasuhisa YAMAMURA, Hiroshi KITAGAWA, Den YOSHIDA, Tadaoki MITANI, and Michio SORAI

Heat capacity of a hydrogen-bonded organic-inorganic hybrid conductor, [Pd(H2-xedag)(Hedag)].TCNQ (x = 1/3) has been precisely measured by adiabatic calorimetry. A very broad but definite anomaly was detected around 170 K and attributed to a metal-insulator transition. The enthalpy and entropy of transition were determined and discussed in relation to a possible order-disorder mechanism of protons in the hydrogen bonds between the Pd complexes and a possible Peierls mechanism. The analysis shows the latter is more likely. The origin of the long superstructure appearing below the metal-insulator transition was suggested being two periodicities arising from the non-stoichiometry x. Some thermodynamic functions are tabulated.
(J. Phys. Soc. Jpn., 68, 3592-3599 (1999))

Heat Capacity of TTF-TCNQ and TSF-TCNQ

Kazuya SAITO, Yasuhisa YAMAMURA, Hiroki AKUTSU, Masaru TAKEDA, Hiromitsu ASAOKA, Hiroyuki NISHIKAWA, Isao IKEMOTO, and Michio SORAI

Heat capacity of TTF-TCNQ was measured by adiabatic and chopped-light ac calorimetries below room temperature. A thermal anomaly due to the Peierls transition of the TCNQ column was clearly detected around 52 K while that due to the TTF column (around 48 K) was not detected in both methods. A small but sharp peak due to the first-order transition at 37 K caused by the phase locking of the CDW's on both columns was detected in calorimetry for the first time. Heat capacity of TSF-TCNQ was measured by adiabatic calorimetry below room temperature. Two steps due to the Peierls transitions on TSF and TCNQ columns were detected. The absence of the anomaly around 48 K in TTF-TCNQ was discussed through comparison of the thermal anomalies of two compounds. Standard thermodynamic functions are tabulated.
(J. Phys. Soc. Jpn., 68, 1277-1285 (1999))

See also M-I Transition in Double-Column Salts

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