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

Journal Article · Tue Nov 03 00:00:00 EST 2015 · Physical Review. B, Condensed Matter and Materials Physics

DOI:https://doi.org/10.1103/PhysRevB.92.174301· OSTI ID:1249065

Mei, A. B. ^[1]; Hellman, O. ^[2]; Schlepuetz, C. M. ^[3]; Rockett, A. ^[1]; Chiang, T. -C. ^[4]; Hultman, L. ^[5]; Petrov, I. ^[6]; Greene, J. E. ^[6]

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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

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 c_v (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 c_v (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 c_p (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 of grazing-incidence (θ ≲ θ_c where θ_c is the density-dependent critical angle) allows selective tuning of x-ray penetration depths to ≲ 10 nm.

• Research Organization: Argonne National Laboratory (ANL), Argonne, IL (United States)
• Sponsoring Organization: Swedish Research Council (VR); USDOE; USDOE Office of Science - Office of Basic Energy Sciences
• Grant/Contract Number: AC02-06CH11357; FG02-07ER46383
• OSTI ID: 1249065
• Alternate ID(s): OSTI ID: 1224920
• Journal Information: Physical Review. B, Condensed Matter and Materials Physics, Journal Name: Physical Review. B, Condensed Matter and Materials Physics Journal Issue: 17 Vol. 92; ISSN 1098-0121
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY