Max-Planck-Inst. Festkoerperforsch., Stuttgart , D-7000, Fed. Rep. Ger.

An ab initio method described earlier (D. Gloetzel et al., 1979) is used for the calcn. of the supercond. crit. temp. Tc and the electron-phonon coupling parameter .lambda. in the title compds. The band structures of these compds. are characterized by strongly hybridizing transition metal d and nonmetal p states. The band structure results are in agreement with earlier APW-X.alpha. calcns. The calcd. .lambda. and Tc values correlate with the no. of valence electrons. Although the av. coupling strength to the light atom is small, a very strong contribution was obsd. of optical phonons to Tc. The discrepancies of the calcd. and exptl. Tc values are not much worse than found previously in elemental metals and can be attributed to deficiencies in the rigid-ion and/or the local-d. approxn.
 

Physical Review B, 55 567-70, 1981.