LATTICE DYNAMICS OF CALCIUM FLUORIDE: PART I. LYDDANE, SACHS, TELLER FORMULA, DIFFUSE X-RAY SCATTERING, AND SPECIFIC HEAT

1962 ◽  
Vol 40 (1) ◽  
pp. 74-90 ◽  
Author(s):  
S. Ganesan ◽  
R. Srinivasan
Keyword(s):  
Specific Heat ◽  
Calcium Fluoride ◽  
Inelastic Neutron Scattering ◽  
Interaction Force ◽  
Inelastic Neutron ◽  
Symmetry Operation ◽  
Absorption Frequency ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

The reported violation of the Lyddane, Sachs, Teller formula in calcium fluoride has been shown to arise from an error due to the non-application of a symmetry operation in the second neighbor fluorine–fluorine interaction in Cribier's work. By correct deduction of the force constants, the diffuse X-ray scattering measurements are shown to be in accord with the Lyddane, Sachs, Teller formula, but the specific heat calculation on this model is in disagreement with the experimental data.Reflection measurements in the infrared and dispersion of refractive index are shown to be consistent with the principal infrared absorption frequency near 40 μ and not near 51 μ as assumed in the previous model. The calculation of the specific heat using this new infrared frequency agreed with the measurements only at very low and very high temperatures.The two curves are brought into agreement by assuming that the non-Coulomb cross interaction force constant β1 between first neighbor calcium and fluorine decrease with the wave vector. The diffuse X-ray scattering was recalculated on the model, which explained the specific heat data, and was again found to be in agreement with the Lyddane, Sachs, Teller formula. It is suggested that detailed infrared and inelastic neutron scattering studies be made on this crystal.

scholarly journals Polycrystalline Time-of-Flight Inelastic Neutron Scattering beyond the Density of States

Proceedings ◽  
2019 ◽  
Vol 26 (1) ◽  
pp. 38
Author(s):  
Leitner
Keyword(s):  
Neutron Scattering ◽  
Density Of States ◽  
Inelastic Neutron Scattering ◽  
Time Of Flight ◽  
Inelastic Neutron ◽  
Single Crystalline ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

Conventionally, experimental phonon dispersions are determined by inelastic neutron scattering on triple-axis spectrometers or by inelastic X-ray scattering, in both cases requiring single crystalline samples. [...]

scholarly journals Lattice Dynamics of Sb 2 Se 3 from Inelastic Neutron and X‐Ray Scattering

2020 ◽  
Vol 257 (6) ◽  
pp. 2000063
Author(s):  
Markus G. Herrmann ◽  
Ralf P. Stoffel ◽  
Ilya Sergueev ◽  
Hans-Christian Wille ◽  
Olaf Leupold ◽  
...  
Keyword(s):  
Lattice Dynamics ◽  
Inelastic Neutron ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

scholarly journals ELECTRON-PHONON INTERACTION IN N-DOPED CUPRATES: AN INELASTIC X-RAY SCATTERING STUDY

2003 ◽  
Vol 17 (04n06) ◽  
pp. 484-492 ◽  
Author(s):  
M. D'ASTUTO ◽  
P. K. MANG ◽  
P. GIURA ◽  
A. SHUKLA ◽  
A. MIRONE ◽  
...  
Keyword(s):  
Phonon Dispersion ◽  
Inelastic Neutron Scattering ◽  
High Temperature Superconductors ◽  
Parent Compound ◽  
Longitudinal Optical ◽  
Small Samples ◽  
Strong Electron ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

Inelastic x-ray scattering (IXS) with very high (meV) energy resolution has become a valuable spectroscopic tool, complementing the well established coherent inelastic neutron scattering (INS) technique for phonon dispersion investigations. In the study of crystalline systems IXS is a viable alternative to INS, especially in cases where only small samples are available. Using IXS, we have measured the phonon dispersion of Nd1.86Ce0.14CuO4 + δ along the [ξ, 0, 0] and [ξ, ξ, 0] in-plane directions. Compared to the undoped parent compound, the two highest longitudinal optical (LO) phonon branches are shifted to lower energies because of Coulomb-screening effects brought about by the doped charge carriers. An additional anomalous softening of the highest branch is observed around q = (0.2, 0, 0). This anomalous softening, akin to what has been observed in other compounds, provides evidence for a strong electron-phonon coupling in the electron-doped high-temperature superconductors.

scholarly journals Polaronic metal phases inLa0.7Sr0.3MnO3uncovered by inelastic neutron and x-ray scattering

2016 ◽  
Vol 93 (4) ◽  
Author(s):  
M. Maschek ◽  
D. Lamago ◽  
J.-P. Castellan ◽  
A. Bosak ◽  
D. Reznik ◽  
...  
Keyword(s):  
Inelastic Neutron ◽  
X Ray ◽  
X Ray Scattering ◽  
Metal Phases ◽  
Ray Scattering

Mixed valence and superconductivity

2007 ◽  
Vol 366 (1862) ◽  
pp. 47-54 ◽  
Author(s):  
Sven Larsson
Keyword(s):  
Potential Energy Surfaces ◽  
Inelastic Neutron Scattering ◽  
Mixed Valence ◽  
Inelastic Neutron ◽  
Intermediate Valence ◽  
Phonon Modes ◽  
X Ray ◽  
X Ray Scattering ◽  
Valence States ◽  
Energy Surfaces

Mixed-valence (MV) systems are referred to here as MV-2 and MV-3 depending on whether two or three consecutive valence states are involved. MV-3 systems range from systems with Hubbard U ≫0, corresponding to a single stable, intermediate valence state, and U ≪0, corresponding to stable alternating valences differing by two units. Experiments using inelastic neutron scattering or inelastic X-ray scattering show softening of breathing phonon modes in MV systems compared with related systems with a single valence. It is hypothesized that softening is due to coupling between potential energy surfaces, corresponding to differing localizations of the electron. As predicted, softening is larger in the delocalized case. A mechanism for superconductivity is suggested.

scholarly journals Phonon dispersion and low-energy anomaly inCaC6from inelastic neutron and x-ray scattering experiments

2010 ◽  
Vol 81 (10) ◽  
Author(s):  
Matteo d’Astuto ◽  
Matteo Calandra ◽  
Nedjma Bendiab ◽  
Geneviève Loupias ◽  
Francesco Mauri ◽  
...  
Keyword(s):  
Phonon Dispersion ◽  
Inelastic Neutron ◽  
Low Energy ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering
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