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.

Structural, Phonon and Thermodynamic Properties of the Rocksalt Structure LiF from First Principles

2016 ◽  
Vol 850 ◽  
pp. 348-353 ◽  
Author(s):  
Hai Jun Hou ◽  
Hao Guan ◽  
Shun Ru Zhang ◽  
Lin Hua Xie ◽  
Lei Wang
Keyword(s):  
Thermodynamic Properties ◽  
Density Of States ◽  
Phonon Dispersion ◽  
Local Density ◽  
Wide Band ◽  
Present Calculation ◽  
Phonon Density ◽  
Phonon Density Of States ◽  
Rocksalt Structure ◽  
Theoretical Results

The structural, electronic, phonon and thermodynamic properties of rocksalt (RS) structure LiF are studied using a plane-wave pseudopotential method within the local density approximation (LDA). The values of lattice constants, elastic constants, and bulk modulus and its pressure derivatives are in well agreement with the available experimental data and other theoretical results. The LiF crystal exhibits a wide band gap of about 8.727 eV. The linear response method is applied to determine the phonon dispersion, phonon density of states and Born effective charge. The phonon frequencies at the Γ, X, L points are analyzed using group theory. We also calculate the thermodynamic functions such as free energy, enthalpy, entropy, specific heat using the phonon density of states. We compare the present calculation results satisfactorily to experimental and previous theoretical results.

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.

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