Infrared study on structural phase transition in (NMe4)2TCNQ3

Hasanudin, Hasanudin; Kuroda, Noritaka; Sugimoto, Toyonari

doi:10.1016/s0379-6779(00)01485-5

Cited by 6 publications

(11 citation statements)

References 2 publications

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“…The frequency of the emv mode remains almost unchanged at low pressures. However, it disappears above 3.6 GPa, in coincidence with the disappearance of the electronic transition band S 1 [1,9]. The pressure dependences of these modes are shown in figure 2.…”

Section: Resultsmentioning

confidence: 71%

Infrared study on pressure-induced charge delocalization in Cs₂TCNQ₃

Hasanudin

Kuroda

Kagayama

et al. 2002

J. Phys.: Condens. Matter

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Pressure dependence of several molecular vibration modes in Cs 2 TCNQ 3 has been observed through infrared absorption measurements. The behaviour of the C-CN and C-H stretching modes suggests that a phase transition takes place at around 3.6 GPa. The π * -electrons, which are localized on TCNQ − molecules in the low-pressure phase, are delocalized significantly in the high-pressure phase. However, the radical-like and neutral-like molecules still coexist in the highpressure phase indicating that the electrons are not completely delocalized. The electron-molecular-vibration coupled mode disappears in the high-pressure phase in coincidence with the disappearance of the inter-radical charge-transfer band S 1 , proving the strong coupling between them.

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Section: Resultsmentioning

confidence: 71%

Infrared study on pressure-induced charge delocalization in Cs₂TCNQ₃

Hasanudin

Kuroda

Kagayama

et al. 2002

J. Phys.: Condens. Matter

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“…In this high-pressure phase, a significant absorption intensity due to the A band seems to extend into the spectral region below 0.2 eV but there is no indication of the Drude tail. The results of the infrared reflectivity measurements up to 7 GPa do not show the Drude spectrum either [9]. In Cs 2 TCNQ 3 the A band is very weak in the unpolarized spectrum, since in this substance the absorption is almost forbidden for the E//a polarization.…”

Section: Resultsmentioning

confidence: 84%

“…Although such phase transition is yet to be studied in Cs 2 TCNQ 3 , Cs 2 TCNQ 3 and (NMe4)2TCNQ3 resemble one another well in the optical properties throughout the near-infrared to visible region. In addition, the infrared absorption spectrum shows that some molecular vibration modes are strongly coupled with the charge transfer electrons in both crystals [3,6].…”

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confidence: 97%

“…Optical absorption and X-ray diffraction studies have shown that second order structural phase transition occurs at 333-338 K in (NMe 4 ) 2 TCNQ 3 [4][5][6]. Although such phase transition is not established yet in Cs 2 TCNQ 3 , Cs 2 TCNQ 3 and (NMe 4 ) 2 TCNQ 3 resemble one another well in the optical properties throughout the near-infrared to visible region.…”

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confidence: 99%

“…Linearly polarized infrared absorption spectra of (NMe 4 ) 2 TCNQ 3 (top) and Cs 2 TCNQ 3 (bottom) at room temperature and ambient pressure broad electronic band designated as A. The results of the infrared reflectivity measurements up to 7 GPa do not show a Drude spectrum either [9]. b-axis.…”

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confidence: 99%

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High Pressure Optical Absorption in Organic Semiconductors (NMe4)2TCNQ3 and Cs2TCNQ3

Hasanudin

Kagayama

Kuroda

et al. 2001

phys. stat. sol. (b)

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The pressure dependence of the optical absorption spectrum in (NMe 4 ) 2 TCNQ 3 and Cs 2 TCNQ 3 has been measured at room temperature in the spectral range from mid-infrared to visible. At the ambient pressure the optical energy gap is observed at around 0.5 and 0.3 eV in (NMe 4 ) 2 TCNQ 3 and Cs 2 TCNQ 3 , respectively. The energy gap in (NMe 4 ) 2 TCNQ 3 decreases by 0.05 eV with increasing pressure up to 2 GPa, followed by an abrupt decrease towards 0.2 eV between 2 and 3 GPa. At higher pressures up to 5.5 GPa the gap remains almost unchanged.The intra-and inter-molecular optical absorption bands in the near-infrared to visible region are intensified by pressure and broadened out at 2.5 GPa. The absorption spectrum in Cs 2 TCNQ 3 exhibits a similar behavior under pressure. These results suggest that an electronic phase transition is induced by pressure at around 2.5 GPa in both substances. This phase transition resembles the charge-order-disorder (Verwey) transition in Fe 3 O 4 in the electronic mechanism.

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