scholarly journals Linear-Response Calculations of Electron-Phonon Coupling Parameters and Free Energies of Defects

1995 ◽  
Vol 408 ◽  
Author(s):  
Andrew A. Quong ◽  
Amy Y. Liu
Keyword(s):  
Linear Response ◽  
Harmonic Approximation ◽  
Linear Response Theory ◽  
Real Space ◽  
Vibrational Properties ◽  
Phonon Coupling ◽  
Free Energies ◽  
Electron Phonon Coupling ◽  
Coupling Parameters ◽  
Average Electron

AbstractLinear-response theory provides an efficient approach for calculating the vibrational properties of solids. Moreover, because the use of supercells is eliminated, points with little or no symmetry in the Brillouin zone can be handled. This allows accurate determinations of quantities such as real-space force constants and electron-phonon coupling parameters. We present highly converged calculations of the spectral function α2F(ω) and the average electron-phonon coupling for Al, Pb, and Li. We also present results for the free energy of vacancy formation in Al calculated within the harmonic approximation.

SUPERCONDUCTIVITY OF SYSTEMS WITH COEXISTING ITINERANT ELECTRONS AND LOCAL PAIRS

2001 ◽  
Vol 15 (23) ◽  
pp. 3125-3142 ◽  
Author(s):  
WOJCIECH R. CZART ◽  
STANISŁAW ROBASZKIEWICZ
Keyword(s):  
Phase Diagrams ◽  
Linear Response ◽  
Linear Response Theory ◽  
Real Space ◽  
Electromagnetic Properties ◽  
Site Density ◽  
Itinerant Electrons ◽  
Interaction Term ◽  
Local Pair ◽  
Local Pairs

Phase diagrams and electromagnetic properties of the system of coexisting itinerant (c)-electrons and localized (d)-electrons which can form real space local pairs are analyzed. The model considered assumes arbitrary value of the on-site density interaction of d-electrons U d , which allows investigation of the effects of reduced d-pair binding energy. The phase diagrams of the system have been evaluated within the approach which treats the on-site interaction term U d exactly and the remaining interactions within the broke symmetry HFA. Within the linear response theory the electromagnetic kernels are calculated and basic superfluid characteristics of the system are determined as a function of electron concentration, interactions and relative position of the bands. Depending on parameters the model is found to exhibit several kinds of superconducting behaviors ranging from the BCS-like to the local pair-like. The relevance of obtained results to the interpretation of experimental data for short-coherence length superconductors is pointed out.

A First-Principles Study of Electron-Phonon Coupling of OsB2

2014 ◽  
Vol 597 ◽  
pp. 113-116
Author(s):  
Yue Qin Wang ◽  
Juan Gao ◽  
Shao Ping Yan
Keyword(s):  
Transition Temperature ◽  
First Principles ◽  
Linear Response ◽  
Lattice Dynamics ◽  
Superhard Material ◽  
Superconducting Transition ◽  
Phonon Coupling ◽  
Phonon Modes ◽  
Electron Phonon Coupling ◽  
Coulomb Pseudopotential

We investigated the lattice dynamics and electron-phonon coupling (EPC) of superhard material OsB2by first-principles linear response calculations. The calculated EPC parameters for the optical phonon modes at Г indicate that the heavy Os atoms play the most important role in deciding the superconducting behavior, and there are sizeable contributions from lighter B atoms to EPC. Our calculated EPC constant is 0.42, and the estimated superconducting transition temperatureTcis 2.1 K using the Coulomb pseudopotentialμ*=0.125, in excellent agreement with the experimental ones.

Investigations of the Thermal Shifts and Electron–Phonon Coupling Parameters of R1 and R2 Lines for Cr3+-doped Forsterite

2014 ◽  
Vol 69 (8-9) ◽  
pp. 497-500 ◽  
Author(s):  
Xiao-Xuan Wu ◽  
Wen-Chen Zheng
Keyword(s):  
Thermal Expansion ◽  
Spectral Lines ◽  
Coupling Coefficients ◽  
Phonon Coupling ◽  
Lattice Thermal Expansion ◽  
Phonon Interaction ◽  
Electron Phonon Interaction ◽  
Electron Phonon Coupling ◽  
Coupling Parameters ◽  
Vibrational Contribution

The thermal shifts of R1 and R2 lines in Cr3+-doped forsterite (Mg2SiO4) are studied by considering both the static contribution due to lattice thermal expansion and the vibrational contribution due to electron-phonon interaction. In the studies, the thermal expansion coefficient of the Cr3+ center is assumed reasonably as that of the corresponding cluster in the host crystal. The results suggest that for R1 and R2 lines the static contributions are opposite in sign and in magnitude about 37% and 45%, respectively, of the corresponding vibrational contributions. The true electron-phonon coupling coefficients α' (obtained by considering both contributions) increase by about 58% and 81%, respectively, for R1 and R2 lines in comparison with the corresponding parameters α obtained by considering only the vibrational contribution. It appears that for the reasonable explanation of thermal shift of spectral lines and the exact estimation of electron-phonon coupling coefficient, both the static and vibrational contributions should be taken into account

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