Optical near-zone-center phonons and their interaction with electrons in YBa2Cu3O7: results of the local-density approximation.

Rodriguez C.O., Liechtenstein A.I., Mazin I.I., Jepsen O., Andersen O.K., Methfessel M.

Ab initio frozen-phonon calculations were performed for YBa2Cu3O7 for the five Ag Raman-active and for two B1u infrared-active optical q=0 modes, with use of the local-density approximation and the full-potential linear-muffin-tin-orbital method. The full Ag dynamical matrix was calculated using 98 k points in the 1/8 Brillouin zone. The theoretical and experimental equilibrium structures and phonon frequencies omega v agree well. Phonon linewidths gamma vq, due to electronic intraband transitions in the normal state, and electron-phonon coupling constants lambda vq identical to gamma vq/( pi N(0) omega v2) were calculated for the Ag modes and small, transverse q. The authors estimate that lambda approximately=1 for the sum over all modes. The phonon shifts and broadenings observed for T 

Physical Review B, 42 2692-5, 1990.

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