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Title: Inner-shell chemistry under high pressure

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Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
OSTI Identifier:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Japanese Journal of Applied Physics; Journal Volume: 56; Journal Issue: 5S3
Country of Publication:
United States

Citation Formats

Miao, Maosheng, Botana, Jorge, Pravica, Michael, Sneed, Daniel, and Park, Changyong. Inner-shell chemistry under high pressure. United States: N. p., 2017. Web. doi:10.7567/JJAP.56.05FA10.
Miao, Maosheng, Botana, Jorge, Pravica, Michael, Sneed, Daniel, & Park, Changyong. Inner-shell chemistry under high pressure. United States. doi:10.7567/JJAP.56.05FA10.
Miao, Maosheng, Botana, Jorge, Pravica, Michael, Sneed, Daniel, and Park, Changyong. Wed . "Inner-shell chemistry under high pressure". United States. doi:10.7567/JJAP.56.05FA10.
title = {Inner-shell chemistry under high pressure},
author = {Miao, Maosheng and Botana, Jorge and Pravica, Michael and Sneed, Daniel and Park, Changyong},
abstractNote = {},
doi = {10.7567/JJAP.56.05FA10},
journal = {Japanese Journal of Applied Physics},
number = 5S3,
volume = 56,
place = {United States},
year = {Wed Apr 19 00:00:00 EDT 2017},
month = {Wed Apr 19 00:00:00 EDT 2017}
  • The local phonon density of states (DOS) at the Sn site in tin monoxide (SnO) is studied at pressures up to 8 GPa with 119Sn nuclear resonant inelastic x-ray scattering (NRIXS) of synchrotron radiation at 23.88 keV. The preferred orientation (texture) of the SnO crystallites in the investigated samples is used to measure NRIXS spectra preferentially parallel and almost perpendicular to the c axis of tetragonal SnO. A subtraction method is applied to these NRIXS spectra to produce projected local Sn DOS spectra as seen parallel and perpendicular to the c axis of SnO. These experimentally obtained local Sn DOSmore » spectra, both in the polycrystalline case as well as projected parallel and perpendicular to the c axis, are compared with corresponding theoretical phonon DOS spectra, derived from dispersion relations calculated with a recently developed shell model. Comparison between the experimental projected Sn DOS spectra and the corresponding theoretical DOS spectra enables us to follow the pressure-induced shifts of several acoustic and optic phonon modes. While the principal spectral features of the experimental and theoretical phonon DOS agree well at energies above 10 meV, the pressure behavior of the low-energy part of the DOS is not well reproduced by the theoretical calculations. In fact, they exhibit, in contrast to the experimental data, a dramatic softening of two low-energy modes, their energies approaching zero around 2.5 GPa, clearly indicating the limitations of the applied shell model. These difficulties are obviously connected with the complex Sn-O and Sn-Sn bindings within and between the Sn-O-Sn layers in the litharge structure of SnO. We derived from the experimental and theoretical DOS spectra a variety of elastic and thermodynamic parameters of the Sn sublattice, such as the Lamb-M{umlt o}ssbauer factor, the mean force constant, and Debye temperatures, as well as the vibrational contributions to the Helmholtz free energy, specific heat, entropy, and internal energy. We found, in part, good agreement between these values, for instance, for the Gr{umlt u}neisen parameters for some selected phonon modes, especially for some optical modes studied recently by Raman spectroscopy. We discuss in detail a possible anisotropy in the elastic parameters resulting from the litharge-type structure of SnO, for instance for the Lamb-M{umlt o}ssbauer factor, where we can compare with existing data from {sup 119}Sn-M{umlt o}ssbauer spectroscopy.« less
  • The structural phase transition of CdSe/ZnS core/shell quantum dots (QDs) has been studied by in situ angle-dispersive X-ray diffraction under high pressure up to 53.6?GPa. The CdSe core transforms from wurtzite to rock-salt structure near 6.3?GPa and then to Cmcm or distorted Cmcm structure probably occurs at 45.1?GPa which has not been observed in CdSe nanomaterials before. The critical pressure from wurtzite to rock-salt and the bulk modulus of rock-salt phase are much higher than those for bulky and uncapped nanoparticle CdSe. The released sample can be kept in rock-salt phase for a certain time, verified by photoluminescence (PL) spectra,more » quite different from the reversible transition for pure CdSe. A reasonable interpretation of the experimental phenomena is given by comparing the bulk modulus of the core and shell and studying the stress sate of the core after decompression. Our study suggests that capping a hard shell is an effective approach to quench the high pressure phase of nanomaterial with a reversible phase transition.« less