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Mączka, Mirosław; Hanuza, J.; Kojima, Seiji

doi:10.1103/physrevb.77.104116

Cited by 9 publications

(5 citation statements)

References 40 publications

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“…These two low-energy optic modes, which show prominent displacement of Ag atoms, are predicted to have negative Gruneisen parameters. Moreover, negative pressure derivative of C 44 is associated with softening of transverse acoustic modes . Thus, pressure-induced phase transformation is likely to be caused by softening of the transverse acoustic mode and the two low-energy soft optic modes.…”

Section: Resultsmentioning

confidence: 99%

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Linear Compressibility and Thermal Expansion of KMn[Ag(CN)₂]₃ Studied by Raman Spectroscopy and First-Principles Calculations

et al. 2013

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We have investigated the linear compressibility and thermal expansion properties of KMn[Ag(CN) 2 ] 3 using Raman spectroscopy and DFT calculations. Phonon frequencies and mode assignments from polarized Raman measurements and DFT calculations agree with each other satisfactorily. Computed linear compressibilities and thermal expansion coefficients corroborate the reported measured values. Pressure variation of mean partial phonon frequencies of KMn[Ag(CN) 2 ] 3 shows that large amplitude anharmonic displacements of Ag atoms can occur with minimum enthalpy cost even with increasing pressure. This means that Ag layer can be squeezed relatively easily, which manifests as PLC in the basal plane and coupled NLC along trigonal axis due to the rigid Mn-NC-Ag-CN-Mn chain along ⟨101⟩ crystal direction. Elastic constants of KMn[Ag(CN) 2 ] 3 indicate that the crystal is highly anisotropic and becomes unstable with increasing pressure. Directional Gruneisen parameters of KMn[Ag(CN) 2 ] 3 are found to be highly anisotropic. These properties show that NLC/NTE and PLC/PTE in KMn[Ag(CN) 2 ] 3 are driven by elastic and Gruneisen anisotropies combined with anharmonic lattice vibrations of Ag atoms. Partial phonon frequencies of KMn[Ag(CN) 2 ] 3 are found to be higher than those of Ag 3 [Co(CN) 6 ]. The partial frequency of K atom increases rapidly with pressure and becomes comparable to that of Ag around 2 GPa. This shows that K inclusion stiffens the lattice and changes the dynamics, causing the pressure-induced phase transformation of KMn[Ag(CN) 2 ] 3 to occur at a higher pressure rather than at 0.2 GPa as in Ag 3 [Co(CN) 6 ]. The phase transformation can be attributed to the softening of two low-energy optic modes (A 2 and E) and the softening of C 44 shear elastic constant and hence the transverse acoustic mode.

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Section: Resultsmentioning

confidence: 99%

“…Moreover, negative pressure derivative of C 44 is associated with softening of transverse acoustic modes. 62 Thus, pressure-induced phase transformation is likely to be caused by softening of the transverse acoustic mode and the two low-energy soft optic modes.…”

Section: Resultsmentioning

confidence: 99%

Linear Compressibility and Thermal Expansion of KMn[Ag(CN)₂]₃ Studied by Raman Spectroscopy and First-Principles Calculations

et al. 2013

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“…Its intensity increases steadily to a maximum at ∼802 K, where is at a minimum, before decaying more rapidly to zero close to T ≈ T c . A Lorentzian profile would be expected for a Debye-type relaxational process, in which case the relaxation time, τ , is given by (Ko et al 2006a, Tsukada et al 2007, Mac ¸zka et al 2008…”

Section: Dynamic Central Peak and Acoustic Mode Couplingmentioning

confidence: 99%

Elastic relaxations associated with the Pm\bar 3 m –R\bar 3 c transition in LaAlO₃: II. Mechanisms of static and dynamical softening

Carpenter¹,

Sinogeikin²,

Bass³

2009

J. Phys.: Condens. Matter

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Brillouin spectra have been collected in situ at temperatures up to ∼1000 K for different crystallographic directions from two single crystal plates of LaAlO(3) perovskite. Elastic moduli derived from these, together with heat capacity, spontaneous strain and Raman data from the literature, have then been used to calibrate the coefficients in a classical Landau free energy expansion for the second order [Formula: see text] phase transition at T(c) = 817 K. The static strain/order parameter coupling model provides a quantitative description of elastic softening between room temperature and ∼700 K, but from ∼700 K up to T(c) additional elastic softening correlates with the development of a central peak in the Brillouin spectra. The presence of quasi-elastic scattering, which reaches maximum intensity ∼5-15 K below T(c), implies a strong dynamical component to the phase transition. Relaxation times estimated from the width of the central peak are of the order of ∼10-100 ps and appear to be more or less constant between ∼700 and 800 K, which is consistent with an intrinsic origin associated with phonon density fluctuations. Central peak width variations and an irregular pattern of acoustic velocity variations in a 20 K temperature interval below T(c) are interpreted in terms of flipping of clusters of tilted octahedra between different ⟨111⟩, ⟨011⟩ and ⟨001⟩ tilt axes. The additional softening beyond that expected from the classical strain/order parameter coupling model can be understood in terms of coupling of acoustic modes with the central peak mode(s).

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“…A similar effect was reported much earlier for Raman lines in [45] for KH 2 AsO 4 and CsH 2 AsO 3 where the origin of the effect was identified as structural hydrogen disorder. Strong asymmetric coupling related to central peak coupling was also reported in K 3 Nb 3 O 6 (BO 3 ) 2 [46]. Their importance stems from the clear distinction between macroscopic mechanical resonances as seen in RUS where the Fano profiles stem from domain boundary dynamics and Raman experiments Downloaded by [University of Saskatchewan Library] at 09:17 02 October 2012 where the signal is related to the bulk.…”

Section: Examples For Breit-wigner/fano Profiles In Hard Mode Spectromentioning

confidence: 81%

Local Symmetry Breaking in the Bulk and in Domain Boundaries: Breit–Wigner Damping of Phonons and Acoustic Resonances

Salje

Carpenter

2012

Ferroelectrics

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High-resolution temperature-dependent Brillouin scattering studies of ferroelectricK3Nb3O6(B
Mirosław Mączka
¹
,
J. Hanuza
²
,
Seiji Kojima
³

Cited by 9 publications

References 40 publications

Linear Compressibility and Thermal Expansion of KMn[Ag(CN)₂]₃ Studied by Raman Spectroscopy and First-Principles Calculations

Linear Compressibility and Thermal Expansion of KMn[Ag(CN)₂]₃ Studied by Raman Spectroscopy and First-Principles Calculations

Elastic relaxations associated with the Pm\bar 3 m –R\bar 3 c transition in LaAlO₃: II. Mechanisms of static and dynamical softening

Local Symmetry Breaking in the Bulk and in Domain Boundaries: Breit–Wigner Damping of Phonons and Acoustic Resonances

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High-resolution temperature-dependent Brillouin scattering studies of ferroelectricK3Nb3O6(BMirosław Mączka1, J. Hanuza2, Seiji Kojima3

Cited by 9 publications

References 40 publications

Linear Compressibility and Thermal Expansion of KMn[Ag(CN)2]3 Studied by Raman Spectroscopy and First-Principles Calculations

Linear Compressibility and Thermal Expansion of KMn[Ag(CN)2]3 Studied by Raman Spectroscopy and First-Principles Calculations

Elastic relaxations associated with the Pm\bar 3 m –R\bar 3 c transition in LaAlO3: II. Mechanisms of static and dynamical softening

Local Symmetry Breaking in the Bulk and in Domain Boundaries: Breit–Wigner Damping of Phonons and Acoustic Resonances

Contact Info

Product

Resources

About

High-resolution temperature-dependent Brillouin scattering studies of ferroelectricK3Nb3O6(B
Mirosław Mączka
¹
,
J. Hanuza
²
,
Seiji Kojima
³

Linear Compressibility and Thermal Expansion of KMn[Ag(CN)₂]₃ Studied by Raman Spectroscopy and First-Principles Calculations

Linear Compressibility and Thermal Expansion of KMn[Ag(CN)₂]₃ Studied by Raman Spectroscopy and First-Principles Calculations

Elastic relaxations associated with the Pm\bar 3 m –R\bar 3 c transition in LaAlO₃: II. Mechanisms of static and dynamical softening