Band structure calculations for Ba$_{6}$Ge$_{25}$ and Ba$_{4}$Na$_{2}$Ge$_{25}$ clathrates

Ivica Zerec; Alexander Yaresko; Peter Thalmeier; Yuri Grin

doi:10.1103/PhysRevB.66.045115

paper

Band structure calculations for Ba $_{6}$ Ge $_{25}$ and Ba $_{4}$ Na $_{2}$ Ge $_{25}$ clathrates

arXiv:cond-mat/0202318 · doi:10.1103/PhysRevB.66.045115

Abstract

Electronic band structures for Ba $_{6}$ Ge $_{25}$ and Ba $_{4}$ Na $_{2}$ Ge $_{25}$ clathrates are calculated using linear muffin-tin orbital method within the local density approximation. It is found that barium states strongly contribute to the density of states at the Fermi level and thus can influence the transport properties of the compounds. A sharp peak of the density of states is found just at the Fermi level. It is also shown that the shifting of barium atoms toward experimentally deduced split positions in Ba $_{6}$ Ge $_{25}$ produces a splitting of this peak which may therefore be interpreted as a band Jahn-Teller effect. If the locking of the barium atoms at the observed structural phase transition is assumed, this reduction of the density of states at the Fermi level can qualitatively account for the experimentally observed decrease of the magnetic susceptibility and electrical resistivity at the phase transition.

9 pages, 8 figures; discussions on Ba4Na2Ge25 and quantitative physical properties extended; resubmitted to Phys. Rev. B

Band structure calculations for Ba6​Ge25​ and Ba4​Na2​Ge25​ clathrates

Abstract

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Band structure calculations for Ba $_{6}$ Ge $_{25}$ and Ba $_{4}$ Na $_{2}$ Ge $_{25}$ clathrates