scholarly journals The Stochastic Self-Consistent Harmonic Approximation: Calculating Vibrational Properties of Materials with Full Quantum and Anharmonic Effects

2021 ◽  
Author(s):  
Lorenzo Monacelli ◽  
Raffaello Bianco ◽  
Marco Cherubini ◽  
Matteo Calandra ◽  
Ion Errea ◽  
...  
Keyword(s):  
Harmonic Approximation ◽  
Vibrational Properties ◽  
Anharmonic Effects ◽  
Self Consistent ◽  
Properties Of Materials ◽  
Full Quantum

scholarly journals Quantum effects in muon spin spectroscopy within the stochastic self-consistent harmonic approximation

2019 ◽  
Vol 3 (7) ◽  
Author(s):  
Ifeanyi John Onuorah ◽  
Pietro Bonfà ◽  
Roberto De Renzi ◽  
Lorenzo Monacelli ◽  
Francesco Mauri ◽  
...  
Keyword(s):  
Muon Spin ◽  
Harmonic Approximation ◽  
Quantum Effects ◽  
Self Consistent ◽  
Muon Spin Spectroscopy

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.

scholarly journals A Self-Consistent Treatment of Damped Motion for Stable and Unstable Collective Modes

1998 ◽  
Vol 07 (02) ◽  
pp. 243-274 ◽  
Author(s):  
H. Hofmann ◽  
D. Kiderlen
Keyword(s):  
Harmonic Approximation ◽  
Linear Response Theory ◽  
Collective Modes ◽  
Fluctuation Dissipation ◽  
Second Moments ◽  
Fluctuation Dissipation Theorem ◽  
Dissipative Tunneling ◽  
Self Consistent ◽  
Path Approximation ◽  
Consistent Treatment

We address the dynamics of damped collective modes in terms of first and second moments. The modes are introduced in a self-consistent fashion with the help of a suitable application of linear response theory. Quantum effects in the fluctuations are governed by diffusion coefficients Dμν. The latter are obtained through a fluctuation dissipation theorem generalized to allow for a treatment of unstable modes. Numerical evaluations of the Dμν are presented. We discuss briefly how this picture may be used to describe global motion within a locally harmonic approximation. Relations to other methods are discussed, like "dissipative tunneling", RPA at finite temperature and generalizations of the "Static Path Approximation".

Non-linear self-consistent screening applied to metallic hydrogen

1979 ◽  
Vol 57 (8) ◽  
pp. 1185-1195 ◽  
Author(s):  
M. D. Whitmore ◽  
J. P. Carbotte ◽  
R. C. Shukla
Keyword(s):  
Harmonic Approximation ◽  
Spherical Approximation ◽  
Face Centered Cubic ◽  
Superconducting Transition ◽  
Metallic Hydrogen ◽  
Proton Proton ◽  
Effective Electron ◽  
Functional Derivatives ◽  
Self Consistent ◽  
Non Linear

Non-linear self-consistent screening of a proton by a high density electron gas has been used to find effective electron–proton potentials for metallic hydrogen for a number of densities and for both face-centered cubic and body-centered cubic structures. The resulting proton–proton potentials have been employed to calculate the phonons in the self-consistent harmonic approximation, following which the effective distributions α2F(ω) were evaluated in the plane wave, spherical approximation. From these, the superconducting transition temperatures Te and functional derivatives were found.Non-linear effects are seen to be important. For both structures, dynamical instabilities occur for rs ≥ 1.0, indicating densities higher than those predicted by linear theory are required. In addition, for the fcc case, Te is enhanced.Te is found to depend sensitively on the structure assumed; for the bcc case, it is very small.For fcc H. McMillan's equation overestimates Te by about 40%, even when λ = 0.5. Leavens' formula agrees with solutions of the Eliashberg gap equations to within about 10%.

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