Arts & Sciences Events
This calendar presented by
Arts & Sciences
[PAST EVENT] Condensed Matter Seminar
June 30, 2015
11am - 12pm
Abstract:
Motivated by experimental activities, recent ab-initio calculations within the framework of the density-functional theory predict the Im-3m structure as the stable superconducting phase of the H3S stoichiometry at the pressure of 200 GPa with the high Tc of about 200 K. The results of our calculation with the hybrid exchange-correlation functional, which is a combination of the exact Hartree-Fock term and the generalized-gradient approximation (GGA), demonstrate a non-negligible influence on the equation of state and on the phonon dispersion, obtained by applying the frozen-phonon approximation. This method does not make it possible to determine the electron-phonon coupling coefficient, which is the essential quantity in the Allen-Dynes equation. Therefore we calculate the respective GGA coupling coefficients on the basis of the linear-response theory and estimate the hybrid values by analyzing the details in the
corresponding electronic band structures. The enhancement of the of the calculated electron-phonon coupling coefficient by more than 20%, and consequently of the Tc, proves an importance of the correlation effects in the investigated material.
Motivated by experimental activities, recent ab-initio calculations within the framework of the density-functional theory predict the Im-3m structure as the stable superconducting phase of the H3S stoichiometry at the pressure of 200 GPa with the high Tc of about 200 K. The results of our calculation with the hybrid exchange-correlation functional, which is a combination of the exact Hartree-Fock term and the generalized-gradient approximation (GGA), demonstrate a non-negligible influence on the equation of state and on the phonon dispersion, obtained by applying the frozen-phonon approximation. This method does not make it possible to determine the electron-phonon coupling coefficient, which is the essential quantity in the Allen-Dynes equation. Therefore we calculate the respective GGA coupling coefficients on the basis of the linear-response theory and estimate the hybrid values by analyzing the details in the
corresponding electronic band structures. The enhancement of the of the calculated electron-phonon coupling coefficient by more than 20%, and consequently of the Tc, proves an importance of the correlation effects in the investigated material.