Electron microscopy study of transition-metal tetrachalcogenide (MSe₄)_nI (M=Nb, Ta)

Crystal Chemistry and Properties of Materials with Quasi-One-Dimensional Structures

“…This was indeed later confirmed by electron diffraction studies [105]. Patterns corresponding to the (a*, c*) plane reveal, at low temperature (90 K), satellite spots very close to the main Bragg spots.…”

“…In order to get some information on the nature of the transition which is observed at 275 K in the resistivity curves, Roucau et al [105] have performed an electron diffraction study. The anomaly in the transport properties is not related to a CDW phenomenon but to a change of the space group corresponding to the disappearing of the glide plane n (i.e.…”

Phonon density of states and low-temperature specific heat of quasi-one-dimensional (TaSe4)2Lorenzo1, Currat2, Dianoux3 et al. 1996Phys. Rev. B18260View full textAdd to dashboardCite

“…While ͑TaSe 4 ͒ 2 I undergoes a Peierls transition 1 ͑T P ϭ250-260 K͒ to a low-temperature charge-density-wave ͑CDW͒ state, 2 ͑NbSe 4 ͒ 3 I is already semiconducting at room temperature. A ferrodistortive structural instability 3,4 occurs at T C ϭ273 K, below which the ͑NbSe 4 ͒ 3 I conductivity is still activated, but with a smaller gap. 3 Electronic band-structure calculations 5 show that the conduction band in both compounds is built from Ta ͑Nb͒ d z 2 orbitals, with overlapping lobes directed along the tetragonal c axis ͑chain axis͒.…”

Giant Dielectric Response in the One-Dimensional Charge-Ordered Semiconductor(NbSe4)3I

“…This new type of ground-state condensate, a charge-density wave (CDW) has first been observed in blue bronze. Iodine doped transition-metal tetraselenides (MSe 4 ) n I with M = Nb, Ta and n = 2, 3, and 10/3, turned out to be paramount examples of materials with one-dimensional electronic structure exhibiting different band fillings [1,2,3,4,5]. For example, (TaSe 4 ) 2 I, (NbSe 4 ) 2 I, and (NbSe 4 ) 10/3 I are metallic at room temperature and undergo classical Peierls transitions with CDW formation at 263 K [6,7], 220 K [7] and 285 K [8] respectively.…”