scholarly journals Lattice Dynamics of YBa2Cu3O6+x (x = 0·25, 0·5, 0.75)

1993 ◽  
Vol 46 (4) ◽  
pp. 535 ◽  
Author(s):  
KK Yim ◽  
J Oitmaa ◽  
MM Elcombe
Keyword(s):  
Oxygen Concentration ◽  
Density Of States ◽  
Coulomb Potential ◽  
Lattice Dynamics ◽  
Short Range ◽  
Phonon Dispersion ◽  
Normal Modes ◽  
Phonon Density ◽  
Phonon Density Of States ◽  
Phonon Dispersion Curves

The lattice dynamics of YBa2Cu306+x with partially filled 0(4) sites is investigated using a supercell method. The model used is the lattice-dynamical shell model, which incorporates the short-range interactions and the long-range Coulomb potential as well as the polarisabilities of ions. Varying the oxygen content produces small changes throughout the spectrum of normal modes, as well as major changes in those modes with large 0(4) amplitudes. Selected phonon dispersion curves are presented, with emphasis on the variation of frequency with oxygen concentration. The nature of new modes, which appear with an increase in oxygen concentration, is investigated. The overall phonon density of states is also presented.

scholarly journals Lattice Dynamics of YBa2Cu3O6+x (x = 0,1)

1992 ◽  
Vol 45 (2) ◽  
pp. 221 ◽  
Author(s):  
KK Yim ◽  
J Oitmaa ◽  
MM Elcombe
Keyword(s):  
Shell Model ◽  
Density Of States ◽  
Normal State ◽  
Lattice Dynamics ◽  
Phonon Dispersion ◽  
Model Parameters ◽  
Phonon Density ◽  
Phonon Density Of States ◽  
Phonon Dispersion Curves ◽  
Least Squares Fit

We report shell model based calculations of the lattice dynamics of YBa2Cu306 and YBa2Cu307. Two models are proposed for YBa2Cu306, the model parameters being obtained by a least squares fit to recent neutron scattering results. The parameters obtained are then used, with modification, to model the lattice dynamics of YBa2Cu307. Since this material has significant carrier concentration, even in the normal state we have used both screened and unscreened versions of the shell model. The screened model gives a better overall description of the lattice dynamics of YBa2Cu307. The phonon dispersion curves along the symmetry directions and the weighted phonon density of states for both YBa2Cu306 and YBa2Cu307 are presented.

LATTICE DYNAMICS OF MBa2Cu3O7(M=Y, Gd) and YBa2Cu3O6

1989 ◽  
Vol 03 (08) ◽  
pp. 1277-1286 ◽  
Author(s):  
JIE QIN ◽  
YIMIN JIANG
Keyword(s):  
Density Of States ◽  
Phonon Dispersion ◽  
Experimental Investigations ◽  
Phonon Density ◽  
Phonon Density Of States ◽  
Phonon Dispersion Curves ◽  
Rare Earth Atom ◽  
Range Overlap ◽  
Phonon Properties ◽  
Good Agreement

We have presented a lattice dynamical calculation of phonon dispersion curves and one-phonon density of states for the high-T c superconducting MBa 2 Cu 3 O x (M=Y, Gd : x=7, 6) compounds. The model we used is in the framework of a rigid-ion model which includes long-range Coulomb potential and a short-range overlap. The results of calculation give quite good agreement with the available Raman and infrared data, and the measurements of phonon density of states. These results therefore can serve as a guide for further experimental investigations of the phonon properties in M-Ba-Cu-O (M=rare earth atom) system.

Thermodynamic properties and lattice dynamics investigation of LuB2C: experiment and ab initio calculations

2019 ◽  
Vol 21 (44) ◽  
pp. 24684-24694 ◽  
Author(s):  
I. R. Shein ◽  
V. V. Novikov ◽  
S. V. Kuznetsov ◽  
K. V. Ponkratov ◽  
A. V. Matovnikov ◽  
...  
Keyword(s):  
Thermodynamic Properties ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Density Of States ◽  
Lattice Dynamics ◽  
Phonon Dispersion ◽  
Phonon Density ◽  
Phonon Density Of States

The phonon dispersion and phonon density of states of LuB2C (Pbam) show the absence of negative phonon frequencies, i.e. this system is dynamically stable.

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