Effective Hamiltonian for potassium dynamics in theβ-pyrochlore superconductor KOs2O6

✍ Scribed by Kuneš, J. ;Pickett, W. E.

• Book ID: 105363761
• Publisher: John Wiley and Sons
• Year: 2006
• Tongue: English
• Weight: 322 KB
• Volume: 203
• Category: Article
• ISSN: 0031-8965
• DOI: 10.1002/pssa.200567138

✦ Synopsis

Abstract

Based on ab initio energies and forces we construct an effective Hamiltonian for anharmonic dynamics of potassium cations in the β ‐pyrochlore compound KOs~2~O~6~. We solve numerically the single‐site problem which is characterized by an extremely flat potential well allowing for large excursions of K‐ions, and illustrate graphically the K‐ion wavefunctions in the four off‐center (symmetry‐breaking) sites. These large displacements from the ideal lattice site result in sizable K–K near‐neighbor interactions through a screened Coulomb interaction. The matrix elements of the interaction in the basis of single‐site eigenstates are calculated and discussed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)