Lattice dynamics of Chevrel phase compounds

Single crystals of the Chevrel phase compounds BaMo6Sg, Cu1.gMo6Sg, Cu3.2Mo6Sg, PbMo6Sg, and SnMo6S8 were prepared by solidification and vapor techniques. Because of the incongruent melting behavior of some of these compounds and because of their high melting points, a pressurized radio-frequency furnace was designed, built, and used for the melt growth of crystals. Crystals as large as 125 mm3 were grown. The energies and symmetries of Brillouin zone-center phonons of these crystals were measured by Raman spectroscopy. These energies are in good agreement with data reported in the literature obtained by measurements of superconducting tunnel junctions. The Raman data, extending over a larger energy range, complement the tunnel-junction data. The Raman data show that the energies of the phonons in these compounds are roughly independent of the particular central metal atom. Small differences in the observed frequency of corresponding phonons in PbMo6Sg, SnMo6Sg, and Cu1.gMo6S8 may be a factor in determining their superconducting transition temperatures. Differences in observed frequencies of corresponding phonons in Cu 1.sMo6Ss and Cu3.2Mo6S8 are correlated with the differences in interatomic distances, and indicate the dominance of sulfur atom motions in these normal modes. Numerical lattice-dynamics calculations were performed. The calculation parameters were varied to fit the experimental data. The results of the calculations include descriptions of the motions of the atoms in the various normal modes, dispersion curves, and phonon density of states curves.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physics

Year dc:date

2011

Author dc:creator

• Holmgren, Donald John

Contributors dc:contributor

• Ginsberg, D.M.

• lattice dynamics
• chevrel phase compounds
• Brillouin zone-center phonons
• Raman spectroscopy

Statement dc:rights

• 1987 Donald John Holmgren

Language dc:language

en

Identifier

1273500

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/25452