Elastic soft mode in perovskite-type layer-structure materials

1980 ◽  
Vol 22 (7) ◽  
pp. 3452-3458 ◽  
Author(s):  
T. Goto ◽  
B. Lüthi ◽  
R. Geick ◽  
K. Strobel
Keyword(s):  
Soft Mode ◽  
Layer Structure ◽  
Type Layer ◽  
Perovskite Type

scholarly journals Erratum: Dynamics of the n‐decylammonium chains in the perovskite‐type layer structure compound (C10H21NH3)2CdCl4) [J. Chem. Phys. 71, 2118 (1979)]

1980 ◽  
Vol 73 (3) ◽  
pp. 1482-1482
Author(s):  
R. Kind ◽  
S. Pleško ◽  
H. Arend ◽  
R. Blinc ◽  
B. Žekš ◽  
...  
Keyword(s):  
Layer Structure ◽  
Chem Phys ◽  
Type Layer ◽  
Perovskite Type

Dynamics of the n-decylammonium chains in the perovskite-type layer structure compound (C10H21NH3)2CdCl4

1979 ◽  
Vol 71 (5) ◽  
pp. 2118 ◽  
Author(s):  
R. Kind ◽  
S. Pleko ◽  
H. Arend ◽  
R. Blinc ◽  
J. Seliger ◽  
...  
Keyword(s):  
Layer Structure ◽  
Type Layer ◽  
Perovskite Type

On ferroelectricity of Sr2Nb2O7and other A2B2O7-type layer-structure crystals

1981 ◽  
Vol 38 (1) ◽  
pp. 849-851 ◽  
Author(s):  
W. Kinase ◽  
S. Nanamatsu ◽  
N. Ishihara ◽  
K. Hasegawa ◽  
K. Yano
Keyword(s):  
Layer Structure ◽  
Type Layer

Low temperature reentrant phase transition in the perovskite type layer compound (C3H7NH3)2PbCl4

1992 ◽  
Vol 40 (1-4) ◽  
pp. 239-247 ◽  
Author(s):  
Y. Abid ◽  
M. Kamoun ◽  
A. Daoud ◽  
F. Romain ◽  
A. Lautie
Keyword(s):  
Phase Transition ◽  
Low Temperature ◽  
Layer Compound ◽  
Type Layer ◽  
Perovskite Type

scholarly journals Neutron diffraction investigation of the temperature dependence of crystal structure and thermal motions of red HgI2

2007 ◽  
Vol 63 (6) ◽  
pp. 828-835 ◽  
Author(s):  
Dieter Schwarzenbach ◽  
Henrik Birkedal ◽  
Marc Hostettler ◽  
Peter Fischer
Keyword(s):  
Crystal Structure ◽  
Neutron Diffraction ◽  
Powder Diffraction ◽  
Soft Mode ◽  
Layer Structure ◽  
Neutron Powder Diffraction ◽  
Force Constants ◽  
Quantum Oscillator ◽  
Thermal Displacement ◽  
Tetrahedral Layer

The structure of, and anisotropic thermal motions in, the red semiconductor tetrahedral layer structure of HgI2 have been studied with neutron powder diffraction as a function of temperature from 10 to 293 K. Average thermal displacement parameters U eq of the two atoms are comparable in size at 10 K, but U eq(Hg) increases considerably faster with temperature than U eq(I), the Hg—I bond being highly non-rigid. The anisotropic displacement tensor U (I) is strongly anisotropic with one term about twice as large as the others, while U (Hg) is nearly isotropic. All displacement tensor elements, except U 22(I), increase faster with temperature than harmonic quantum oscillator curves indicating a softening of the isolated-atom potentials at large amplitudes. A lattice dynamical model provides arguments that the anisotropic thermal motions of I are dominated by a soft mode with a wavevector at the [½ ½ 0] boundary of the Brillouin zone consisting essentially of coupled librations of the HgI4 tetrahedra, and by translations of the entire layer. The large vibration amplitudes of Hg suggest weak Hg–I force constants compared with the I–I force constants, allowing Hg to move quite freely inside the tetrahedra. The libration mode induces dynamic deformations of the Hg—I bond with twice its frequency. This provides a mechanism for the anharmonicity and may explain the lightening of the color from red to orange upon cooling at ca 80 K.

Phonon dispersion in the perovskite-type layer material K2ZnF4

1983 ◽  
Vol 115 (2) ◽  
pp. 463-470 ◽  
Author(s):  
H. Rauh ◽  
R. Geick ◽  
N. Lehner ◽  
J. Bouillot ◽  
G. Eckold
Keyword(s):  
Phonon Dispersion ◽  
Layer Material ◽  
Type Layer ◽  
Perovskite Type
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