The Raman spectrum of NaCN under hydrostatic pressure

Dultz, W.; Krause, Hans; Winchester, L. W.

doi:10.1063/1.435223

Cited by 19 publications

(7 citation statements)

References 14 publications

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“…Since no other spectroscopic changes accompany this phenomenon it is probable that it merely indicates that the pressure dependence of v(CN) is non-linear, rather than a structural change. We note that the initial slope of the v(CN) plot is close to that found for CN-doped NaCl, 0.54 cm-' kbar-1,25 at 90 K. However, Dultz et al 23 have very recently reported dco/dP of 0.9 cm-l kbar-I for NaCN (11) in the range up to 6 kbar : the reason for the discrepancy is not clear.…”

Section: ( Wsupporting

confidence: 63%

Vibrational spectroscopy at very high pressures. Part 22.—Raman study of sodium and potassium cyanides

Adams¹,

Sharma²

1978

J. Chem. Soc., Faraday Trans. 2

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Raman spectra of KCN have been investigated up to z 55 kbar and NaCN to W 37 kbar. KCN (111) shows no distinct lattice mode spectrum and, in this respect, is similar to cubic KCN (I). KCN (IV) shows only a broad doublet, interpreted as due to both libratory and translatory motions, but distinguished from the behaviour of the Bl-related phases in being at much higher frequency. The behaviour of the single v(CN) band found for each phase has been studied as a function of pressure Values of dw/dP (cm-l kbar-') are : KCN (I) at 20°C, 0.50 ; KCN (I) at llO"C, 0.574 ; KCN 011) at llO"C, 0.45 ; KCN (IV) at 20"C, 0.32.Results for NaCN confirm those recently reported for pressures up to 6 kbar but extend them to much higher pressures. For NaCN (11) dw/dP(cm-l kbar-') is 0.57 up to 21 kbar but is reduced to 0.45 above that pressure. There is a similar change of slope at 21 kbar in the frequency against pressure plot for the two lowfrequency bands but this is thought not to have structural significance.

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Section: ( Wsupporting

confidence: 63%

Vibrational spectroscopy at very high pressures. Part 22.—Raman study of sodium and potassium cyanides

Adams¹,

Sharma²

1978

J. Chem. Soc., Faraday Trans. 2

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“…These values, which were obtained by Brillouin scattering experiments in a range of hydrostatic pressure up to several kbar, agree fairly well with our results. Raman spectra of NaCN and KCN under hydrostatic pressure have been studied by Dultz, Krause & Winchester (1977) and Dultz & Krause (1978). These authors derived Grtineisen parameters for the transverse-acoustical soft mode connected with c44, without giving further details of nonlinear elastic properties.…”

Section: Discussionmentioning

confidence: 99%

Third-order elastic constants of cubic sodium cyanide and potassium cyanide

Haussühl¹,

Michaelis²

1979

Acta Cryst Sect A

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“…Raman spectroscopy is often useful to infer longer unit cell (Brillouin zone folding) of phase involved in a crystallographic phase transition. If a vibrational branch (such as a longitudinal optical vibration) is subject to n folds of its Brillouin zone, it will give rise to n-1 new evenly spaced vibrations of comparable intensity [7,29]. Suppose the unit cell approximately doubles along c axis at low temperature T. This will permit Raman spectra of one extra very low frequency optical phonon, which would be described as the Brillouin zone boundary in the high-T phase.…”

Section: Raman Spectroscopymentioning

confidence: 99%

Structural phase transitions in the geometric ferroelectric LaTaO4

et al. 2021

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The recent report of an intermediate incommensurately modulated orthorhombic phase in LaTaO 4 has prompted a re-examination of the phase transition sequence in LaTaO 4 as a function of temperature. With falling temperature, the sequence of phases examined is (orthorhombic) Cmc2 1 (C) ↔ Cmc2 1 (IC) ↔ (monoclinic)P2 1 /c, with C and IC denoting commensurate and incommensurate phases, respectively. The orthorhombic to monoclinic transition, T m−o , is a first order reconstructive transition occurring at 440 K and T IC−C is a first-order displacive transition occurring at 500-530 K. Strain and elasticity data confirm a first-order transition between the basic and modulated Cmc2 1 phases, with similarities to the isostructural fluoride BaMnF 4 . A Raman spectroscopic study of the LaTaO 4 phase transition indicates that the IC-C phase transition is driven by a soft zone-boundary phonon (unstable) of the commensurate orthorhombic (Cmc2 1 ) phase. The soft phonon is found to appear (underdamped) above 443 K and vanishes (overdamped) around 528 K. A large supercell of the monoclinic phase below T m−o is proposed based on the Raman spectroscopic results.

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The Raman spectrum of NaCN under hydrostatic pressure

Cited by 19 publications

References 14 publications

Vibrational spectroscopy at very high pressures. Part 22.—Raman study of sodium and potassium cyanides

Vibrational spectroscopy at very high pressures. Part 22.—Raman study of sodium and potassium cyanides

Third-order elastic constants of cubic sodium cyanide and potassium cyanide

Structural phase transitions in the geometric ferroelectric LaTaO4

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