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Title: Reflection thermal diffuse x-ray scattering for quantitative determination of phonon dispersion relations

Synchrotron reflection x-ray thermal diffuse scattering (TDS) measurements, rather than previously reported transmission TDS, are carried out at room temperature and analyzed using a formalism based upon second-order interatomic force constants and long-range Coulomb interactions to obtain quantitative determinations of MgO phonon dispersion relations (h) over bar omega(j) (q), phonon densities of states g((h) over bar omega), and isochoric temperature-dependent vibrational heat capacities cv (T). We use MgO as a model system for investigating reflection TDS due to its harmonic behavior as well as its mechanical and dynamic stability. Resulting phonon dispersion relations and densities of states are found to be in good agreement with independent reports from inelastic neutron and x-ray scattering experiments. Temperature-dependent isochoric heat capacities cv (T), computed within the harmonic approximation from (h) over bar omega(j) (q) values, increase with temperature from 0.4 x 10-4 eV/atom K at 100 K to 1.4 x 10-4 eV/atom K at 200 K and 1.9 x 10-4 eV/atom K at 300 K, in excellent agreement with isobaric heat capacity values cp (T) between 4 and 300 K. We anticipate that the experimental approach developed here will be valuable for determining vibrational properties of heteroepitaxial thin films since the use ofmore » grazing-incidence (θ ≲ θc where θc is the density-dependent critical angle) allows selective tuning of x-ray penetration depths to ≲ 10 nm.« less
Authors:
 [1] ;  [2] ;  [3] ;  [1] ;  [4] ;  [5] ;  [6] ;  [7]
  1. Univ. of Illinois, Urbana, IL (United States). Department of Materials Science and the Materials Research Laboratory
  2. California Inst. of Technology (CalTech), Pasadena, CA (United States). Department of Applied Physics and Materials Science
  3. Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS); Paul Scherrer Inst. (PSI), Villigen (Switzerland). Swiss Light Source
  4. Univ. of Illinois, Urbana, IL (United States). Department of Physics and the Materials Research Laboratory
  5. Linkoping Univ., Linkoping (Sweden). Dept. of Physics
  6. Univ. of Illinois, Urbana, IL (United States). Department of Materials Science and the Materials Research Laboratory; Linkoping Univ., Linkoping (Sweden). Dept. of Physics
  7. Univ. of Illinois, Urbana, IL (United States). Department of Materials Science and the Materials Research Laboratory; Linkoping Univ., Linkoping (Sweden). Dept. of Physics
Publication Date:
OSTI Identifier:
1249065
Grant/Contract Number:
AC02-06CH11357; FG02- 07ER46383; SFO Mat-LiU
Type:
Accepted Manuscript
Journal Name:
Physical Review. B, Condensed Matter and Materials Physics
Additional Journal Information:
Journal Volume: 92; Journal Issue: 17; Journal ID: ISSN 1098-0121
Publisher:
American Physical Society (APS)
Research Org:
Argonne National Laboratory (ANL), Argonne, IL (United States)
Sponsoring Org:
USDOE Office of Science - Office of Basic Energy Sciences; Swedish Research Council (VR)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY