Observation of a phase transition in ThBr4 and ThCl4 single crystals by far-infrared and Raman spectroscopy study

Hubert, S.; Delamoye, P.; Lefrant, S.; Lepostollec, M.; Hussonnois, M.

doi:10.1016/0022-4596(81)90189-4

Cited by 53 publications

(21 citation statements)

References 11 publications

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“…Below 92 K, j3-ThBr4 displays Splitting of a Raman Vibration and of a bromine nuclear quadrupole resonance line, and new X-ray and neutron diffraction lines appear [2,7]. These observations are not consistent with any conventional superlattice of the tetragonal unit cell, and are caused by a second-order phase transition in which bromine atoms along the c ciystallographic axis are displaced sinusoidally from their sites with a repeating distance of 3.201 c. This phenomenon is a subject of intense investigation and illustrates how careful measurements on pure, Single ciystals can reveal new scientific ideas.…”

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confidence: 99%

Advances in Chemistry of the Actinide Elements

Morss

1984

Radiochimica Acta

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Recent research accomplishments that elucidate the bonding and reactivity of the actinides are highlighted in this review. Improved syntheses of protactinium and transplutonium metals and Compounds have led to determination of physical properties that reveal effects of 5f interactions. Theimodynamic measurements on metals, aqueous ions, and oxides have yielded more systematic understanding of the chemistry of the entire actinide series. Advances in bonding include the preparation of new organoactinide Compounds with strong a and TT metal-carbon and metal-hydrogen bonds; the development of new actinide complexing, sequestering, and extracting agents; and the study of chemical consequences of radioactive decay on oxides and halides. New techniques that impact actinide chemistry are laser fluorescence and photochemistry, radiocoulometry, and pulse radiolysis. Progress has also been made in outlining the basic chemical behavior of the heaviest actinides and the transactinides.Two isomorphs of ThBr4 are known, the well-known /3-ThBr4 and a low-temperature, poorly-characterized a-ThBr4. Below 92 K, j3-ThBr4 displays Splitting of a Raman Vibration and of a bromine nuclear quadrupole resonance line, and new X-ray and neutron diffraction lines appear [2,7]. These observations are not consistent with any conventional superlattice of the tetragonal unit cell, and are caused by a second-order phase transition in which bromine atoms along the c ciystallographic axis are displaced sinusoidally from their sites with a repeating distance of 3.201 c. This phenomenon is a subject of intense investigation and illustrates how careful measurements on pure, Single ciystals can reveal new scientific ideas.

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confidence: 99%

Advances in Chemistry of the Actinide Elements

Morss

1984

Radiochimica Acta

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“…Many of the properties of ThBr 4 also apply to ThCl 4 because of the structural isomorphism of the two compounds at RT and the same phase transition which both substances undergo at low temperature [18,24], Finally, we may say that ThBr 4 , which was a forgotten compound ten years ago, is of new and increasing interest to the fields of solid state physics and chemistry and more particularly to the field of spectrochemistry of the tetravalent actinides.…”

Section: Resultsmentioning

confidence: 99%

“…The first evidence for the phase transition came from the unambiguous splitting of the 122 cm" 1 E g active Raman vibration and other vibrational modes [18], the second from the observation of an active Raman soft mode of the low temperature phase with energy ranging from 0 at T 0 to 20 cm" 1 at 4.2 Κ [18] according to a law of the type ν = A (T 0 -T) 1 . All experiments were carried out with single crystals.…”

Section: Evidence For 0-thbr 4 Phase Transitionmentioning

confidence: 99%

“…The five inactive modes are of ungerade symmetry and, as we shall see later, one of them has been observed through inelastic neutron diffusion. The energy of active modes ranges from 38 to 194cm" 1 [18].…”

Section: Phonon Spectramentioning

confidence: 99%

“…Over the 20 modes, the 10 ungerade Raman active and the 5 ungerade infrared active spectra of large oriented single crystals have been identified and their energy has been measured [18] at RT. The longitudinal optical mode of the symmetry E u has also been measured.…”

Section: Phonon Spectramentioning

confidence: 99%

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Thorium Tetrabromide: An Old Compound Restudied by Actinide Chemistry

Guillaumont

1983

Radiochimica Acta

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Crystallogenesis /Luminescence /Radioluminescence /Commensurate-incommensurate phase transition /Absorption spectroscopy/ Emission spectroscopy/Tetravalent actinidesAbstract Some properties of thorium tetrabromide which have become apparent since 1975 are examined. Until the discovery of its radioluminescence, no particular attention was given to this halide, but subsequently research on this compound was intensified.Owing to the exceptional radioresistance of the material, studies concerning the possibilities of using ThBr 4 as a radiation detector, a target detector for nuclear reactions and a converter of nuclear energy into luminous energy have been given priority. Later, its use as a matrix for high resolution spectroscopy of M 4+ actinide ions (because of the properties of the Th 4+ ) ion was considered. The interpretation of the absorption and emission spectra required a complete characterization of vibrational and structural properties of ThBr 4 , especially at low temperature. It was only then discovered that ThBr 4 underwent a commensurate -incommensurate phase transition towards 90 Κ and that the modulated phase still existed at 4 K. Extensive research was begun which later expanded into numerous fields; some of these, such as phase transitions dynamics and the effect of the incommensurability on spectroscopic and thermodynamic properties are presently under study. Much of this work required the availability of large (several cm 3 ) single crystals of ThBr 4 and consequently production of this compound on the kilogram scale was carried out.

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Vibrational study of crystal phase transitions in pyrrole (C₄H₅N) and C₄D₅N

Lautié¹,

Romain²

1990

J Raman Spectroscopy

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Infrared and Raman spectra of crystalline pyrrole and pyrrole-d5 were recorded in the range M O O 0 cm-'. The behaviour of internal and external modes was studied as a function of temperature between 200 and 5 K. Two phase transitions were observed at 67 and 30 K and their mechanism is discussed. For the incommensurate phase, between 67 and 30 K, the amplitude and phase modes were identified at about 20 and 10 cm-', respectively; for the first, a critical expownt of 030 was determined. No evidence of NH R hydrogen bond participation in the transitions has been detected.

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Observation of a phase transition in ThBr4 and ThCl4 single crystals by far-infrared and Raman spectroscopy study

Cited by 53 publications

References 11 publications

Advances in Chemistry of the Actinide Elements

Advances in Chemistry of the Actinide Elements

Thorium Tetrabromide: An Old Compound Restudied by Actinide Chemistry

Vibrational study of crystal phase transitions in pyrrole (C₄H₅N) and C₄D₅N

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Observation of a phase transition in ThBr4 and ThCl4 single crystals by far-infrared and Raman spectroscopy study

Cited by 53 publications

References 11 publications

Advances in Chemistry of the Actinide Elements

Advances in Chemistry of the Actinide Elements

Thorium Tetrabromide: An Old Compound Restudied by Actinide Chemistry

Vibrational study of crystal phase transitions in pyrrole (C4H5N) and C4D5N

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Vibrational study of crystal phase transitions in pyrrole (C₄H₅N) and C₄D₅N