Phase and amplitude modes of the<i>n=4</i>incommensurate phase II of biphenyl: Neutron scattering experiments and theoretical results

Launois, Pascale; Moussa, F.; Lemée-Cailleau, MH; Cailleau, H.

doi:10.1103/physrevb.40.5042

Cited by 29 publications

(25 citation statements)

References 28 publications

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“…ever a similar anisotropy is often seen in other molecular crystals. 14,15,24 The D i coefficients exhibit an unexpected temperature dependence ͑see Table I͒ which undoubtedly results from the SM coupling to the TA modes at least in the (a ជ *,b ជ *) plane. This effect is independently seen from the thermal dependence of 2 (q ជ ) at different wave vectors ͑Fig.…”

Section: Soft-mode Dispersion Curvementioning

confidence: 99%

Pretransitional dynamics of the structural phase transition in anthracene-TCNB: A comparison of Raman-scattering and inelastic-neutron-scattering experiments

et al. 1996

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We report on the study of the pretransitional dynamics of the structural phase transition in anthracene-TCNB by Raman scattering and inelastic neutron scattering at atmospheric pressure. This mixed-stack charge-transfer molecular crystal presents an antiferrodistorsive structural phase transition ͑SPT͒ corresponding to the reorientation of the anthracene molecules in their molecular plane. The dynamical regime of this SPT appears to be mainly displacive. However, our measurements clearly show different behavior of soft mode parameters in both phases. This particularity could be interpreted in terms of an intermediate regime between displacive and order-disorder regimes as was proposed in a coupled double-well potential model ͓S. Aubry, J. Chem. Phys. 64, 3392 ͑1976͔͒. An intense central peak is also found in the neutron spectra just above the transition temperature. It presents a critical behavior in Q space clearly different from the soft-mode one.

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Section: Soft-mode Dispersion Curvementioning

confidence: 99%

Pretransitional dynamics of the structural phase transition in anthracene-TCNB: A comparison of Raman-scattering and inelastic-neutron-scattering experiments

et al. 1996

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“…Structural phase transitions have been studied extensively in biphenyl, [3][4][5][6][7][8][9] p-terphenyl, [10][11][12][13][14][15][16][17][18][19][20] p-quaterphenyl, 13,21,22 and p-hexaphenyl. 23 In the case of biphenyl and quaterphenyl, there is agreement that the twisted conformation belongs to the D 2 symmetry group.…”

Section: Introductionmentioning

confidence: 99%

Conformation of p-terphenyl under hydrostatic pressure

Zhuravlev

McCluskey

2004

The Journal of Chemical Physics

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The conformation of p-terphenyl (C18H14) and deuterated p-terphenyl (C18D14) has been investigated, using high-pressure infrared spectroscopy at liquid-helium temperatures. First-principles calculations, together with the experimental results, were performed to determine the structure of p-terphenyl in the twisted conformation. At low temperatures and pressures, p-terphenyl belongs to the C2 point group of symmetry. In this configuration, the central ring is twisted with respect to the plane of the outer rings. The symmetry of the molecule is nearly C2h, consistent with previous x-ray diffraction measurements.

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“…Experimentally, this last property explains why phason modes are so efficient to the spin-lattice relaxation rate in NMR spectroscopy and indeed many incommensurate phases where discovered by this technique. However, coherent neutron scattering was the unique way to measure the phason spectral function getting by the way frequency dispersion and damping of this excitation [15,[38][39][40][41].…”

Section: Incommensurate Modulated Crystalsmentioning

confidence: 99%

Crystallography and dynamics in superspace

et al. 2017

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Abstract. The discovery in materials of long range order without lattice periodicity has generated a very broad field of research with the introduction of totally new concepts. The common feature of this new state of matter is the translational symmetry recovered by adding supplementary dimensions to the physical space, defining a crystallographic superspace. Along these supplementary directions, specific low excitations, so-called phasons, are predicted and observed. These quasi-periodic crystals may present phase transitions as function of external parameters, which have then to be described as symmetry breakings within these crystallographic superspaces. Three different families of quasi-periodic crystals are usually considered: incommensurate modulated crystals, aperiodic composites and quasicrystals. Their crystallography and dynamics are discussed.

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Phase and amplitude modes of then=4incommensurate phase II of biphenyl: Neutron scattering experiments and theoretical results

Cited by 29 publications

References 28 publications

Pretransitional dynamics of the structural phase transition in anthracene-TCNB: A comparison of Raman-scattering and inelastic-neutron-scattering experiments

Pretransitional dynamics of the structural phase transition in anthracene-TCNB: A comparison of Raman-scattering and inelastic-neutron-scattering experiments

Conformation of p-terphenyl under hydrostatic pressure

Crystallography and dynamics in superspace

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