Abstract
Using the local-density approximation and the full-potential linear muffin-tin-orbital method we have calculated the total energy of for x=0 and 0.5 as a function of tilting and breathing distortions. For x=0 we find an instability for a combination of both distortions and we correctly reproduce the monoclinic structure. For x=0.5 we correctly find the cubic phase to be stable. The frequencies of the tilting and breathinglike phonons are calculated for x=0 and 0.5. In the cubic structure we calculate the strength of the electron-phonon coupling for the breathing mode as a function of x using a rigid-band approximation. For 0.37<x<0.5, ≊0.3 and follows the trend of . The superconductivity is conceivably mediated by the electron-phonon coupling.
- Received 24 June 1991
DOI:https://doi.org/10.1103/PhysRevB.44.5388
©1991 American Physical Society