Reflection thermal diffuse x-ray scattering for quantitative determination of phonon dispersion relations
2015 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 92, no 17, 174301- p.Article in journal (Refereed) Published
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 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 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 (theta less than or similar to theta(c), where theta(c) is the density-dependent critical angle) allows selective tuning of x-ray penetration depths to less than or similar to 10 nm.
Place, publisher, year, edition, pages
AMER PHYSICAL SOC , 2015. Vol. 92, no 17, 174301- p.
Condensed Matter Physics
IdentifiersURN: urn:nbn:se:liu:diva-123062DOI: 10.1103/PhysRevB.92.174301ISI: 000364013100002OAI: oai:DiVA.org:liu-123062DiVA: diva2:876659
Funding Agencies|Swedish Research Council (VR) [2014-5790, 2013-4018]; Swedish Government Strategic Research Area (SFO) in Materials Science on Advanced Functional Material (MatLiU AFM) [2009-00971]; US Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences [DE-FG02-07ER46383]; DOE Office of Science, Argonne National Laboratory [DE-AC02-06CH11357]2015-12-042015-12-032016-08-31