Phonon density of states and oxygen-isotope effect in Ba sub 1 minus x K sub x BiO sub 3

Journal Article · Tue Mar 31 23:00:00 EST 1992 · Physical Review, B: Condensed Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.45.8052· OSTI ID:7234666

Loong, C ^[1]; Vashishta, P; Kalia, R K; Jin, W; Degani, M H ^[2]; Hinks, D G; Price, D L; Jorgensen, J D; Dabrowski, B; Mitchell, A W; Richards, D R; Zheng, Y ^[3]

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1. Intense Pulsed Neutron Source, Argonne National Laboratory, Argonne, Illinois 60439-4814 (United States)
2. Concurrent Computing Laboratory for Materials Simulations and Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803-4001 (United States)
3. Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439-4843 (United States)

The phonon densities of states (DOS) of insulating BaBiO{sub 3} and superconducting Ba{sub 0.6}K{sub 0.4}BiO{sub 3} and the variation of the phonon spectrum of the superconducting compound upon oxygen-isotope ({sup 16}O, {sup 18}O) substitution are determined by inelastic neutron scattering (INS) and molecular-dynamics (MD) simulations. The MD simulations are carried out with an effective interaction potential which includes steric effects, Coulomb interactions, and the charge-dipole interactions due to the electronic polarizability of O{sup 2{minus}}. The MD results are in good agreement with the INS experiments and electron-tunneling measurements. Partial DOS of Ba, K, Bi, and O in BaBiO{sub 3} and Ba{sub 0.6}K{sub 0.4}BiO{sub 3} are also determined from MD simulations. In the superconducting material, the phonon spectrum softens and is comprised of broad bands around 15, 30, and 60 meV. The partial DOS reveal that phonons above 20 meV are due to oxygen vibrations, whereas phonons below 20 meV are due to Ba, K, and Bi. The reference oxygen-isotope-effect exponent, {alpha}{sub O}{ital r}={minus}{partial derivative} ln{l angle}{omega}{r angle}/{partial derivative} ln{ital M}{sub O}, of Ba{sub 0.6}K{sub 0.4}BiO{sub 3} is determined to be {alpha}{sub O}{ital r}=0.42{plus minus}0.05 from the mass ({ital M}{sub O}) variation of the first moment of the phonon DOS, {sup 16}{sub O}{l angle}{omega}{r angle} and {sup 18}{sub O}{l angle}{omega}{r angle}.

• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 7234666
• Journal Information: Physical Review, B: Condensed Matter; (United States), Journal Name: Physical Review, B: Condensed Matter; (United States) Vol. 45:14; ISSN 0163-1829; ISSN PRBMD
• Country of Publication: United States
• Language: English

Related Subjects

665411* -- Basic Superconductivity Studies-- (1992-)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALKALI METAL COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
BARIUM OXIDES
BISMUTH COMPOUNDS
BISMUTH OXIDES
CHALCOGENIDES
COUPLING
CRITICAL TEMPERATURE
ELECTRON-PHONON COUPLING
ELEMENTS
ENERGY-LEVEL DENSITY
HIGH-TC SUPERCONDUCTORS
ISOTOPE EFFECTS
NONMETALS
OXIDES
OXYGEN
OXYGEN COMPOUNDS
PHONONS
PHYSICAL PROPERTIES
POTASSIUM COMPOUNDS
POTASSIUM OXIDES
QUASI PARTICLES
SUPERCONDUCTORS
THERMODYNAMIC PROPERTIES
TRANSITION TEMPERATURE