Surface phonon modes of the RbBr(001) crystal surface by inelastic He-atom scattering

Journal Article · Thu Jun 15 04:00:00 EDT 1989 · Phys. Rev. B: Condens. Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.39.12838· OSTI ID:6257533

Chern, G; Skofronick, J G; Brug, W P; Safron, S A

Inelastic He-atom scattering (/ital k//sub /ital i//approx.7A/sup /minus/1/) was used to measure the dynamics of theRbBr(001) crystal surface (/ital T//sub /ital s//approx.115 K). Time-of-flight spectrataken in two high-symmetry directions, <100> and<110>, were analyzed to give the surface dispersion curves forthe entire surface Brillouin zones /Gamma/bar // /ital X/bar // and /Gamma/bar // /ital M/bar //. TheRayleigh mode and its geometric ''folded,'' optical surface resonance (expectedfrom the quasimonatomic behavior due to the nearly equal masses of theRb/sup +/ and Br/sup /minus// ions) were observed; the data alsosuggest the existence of another optical surface feature in the optical band.Although calculations had suggested that this crystal should have importantsurface relaxation effects, the main one being a surface-localized opticalbranch lying above the optical band, no evidence of this was seen. Moreover,the calculated surface dispersion curves for the unrelaxed surface appear tofit the measurements slightly better than those for the relaxed surface,although neither predicts the optical resonance mentioned above. Finally, theseobserved differences provide guidance on the use of the shell model fordescribing the physics of ionic insulator crystals.

• Research Organization: Department of Physics, Florida State University, Tallahassee, Florida 32306-3016(US); Center for Materials Research and Technology (MARTECH), Florida State University, Tallahassee, Florida 32306-3016; Department of Chemistry, Florida State University, Tallahassee, Florida 32306-3006; Center for Materials Research and Technology (MARTECH), Florida State University, Tallahassee, Florida 32306-3016
• OSTI ID: 6257533
• Journal Information: Phys. Rev. B: Condens. Matter; (United States), Journal Name: Phys. Rev. B: Condens. Matter; (United States) Vol. 39:17; ISSN PRBMD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360603* -- Materials-- Properties
ALKALI METAL COMPOUNDS
BRILLOUIN ZONES
BROMIDES
BROMINE COMPOUNDS
COLLISIONS
CRYSTAL FACES
CRYSTALS
DISPERSION RELATIONS
ELEMENTS
ENERGY SPECTRA
FLUIDS
GASES
HALIDES
HALOGEN COMPOUNDS
HELIUM
LATTICE VIBRATIONS
NONMETALS
PHONONS
QUASI PARTICLES
RARE GASES
RUBIDIUM BROMIDES
RUBIDIUM COMPOUNDS
SPECTRA
SURFACE PROPERTIES
TIME-OF-FLIGHT METHOD
ZONES