Chen, Shuonan; Coleman, Devin; Abernathy, Douglas L; Banerjee, Arnab; Daemen, Luke L; Mangolini, Lorenzo; Li, Chen W Giant low-temperature anharmonicity in silicon nanocrystals Journal Article Phys. Rev. Materials, 4 , pp. 056001, 2020. Abstract | Links | BibTeX | Tags: anharmonicity, high temperature, lifetime, neutron @article{Li2020, title = {Giant low-temperature anharmonicity in silicon nanocrystals}, author = {Shuonan Chen and Devin Coleman and Douglas L. Abernathy and Arnab Banerjee and Luke L. Daemen and Lorenzo Mangolini and Chen W. Li}, url = {https://journals.aps.org/prmaterials/pdf/10.1103/PhysRevMaterials.4.056001}, doi = {10.1103/PhysRevMaterials.4.056001}, year = {2020}, date = {2020-05-04}, journal = {Phys. Rev. Materials}, volume = {4}, pages = {056001}, abstract = {The phonon density of states of silicon nanocrystals with size between 4 and 7.5 nm was measured by inelastic neutron scattering in the 5-600 K temperature range. The narrow particle size distributions enable the study of size effects on phonon dynamics. Giant softening of phonon features below 30 meV, universal broadening of phonon features, and the disappearance of intermediate-energy phonons were observed with decreasing nanocrystals size. Such size effects are mostly attributed to the structure variations within the nanocrystals. The phonons below 30 meV in silicon nanocrystals show temperature dependence opposite to the bulk silicon, explained by the large anharmonicity of the under-constrained near-surface phonons. This is supported by the abnormal atomic mean-square-displacement, and low energy phonon population in small silicon nanocrystals. This work provides crucial information on the phonon dynamics in spatially confined materials.}, keywords = {anharmonicity, high temperature, lifetime, neutron}, pubstate = {published}, tppubtype = {article} } The phonon density of states of silicon nanocrystals with size between 4 and 7.5 nm was measured by inelastic neutron scattering in the 5-600 K temperature range. The narrow particle size distributions enable the study of size effects on phonon dynamics. Giant softening of phonon features below 30 meV, universal broadening of phonon features, and the disappearance of intermediate-energy phonons were observed with decreasing nanocrystals size. Such size effects are mostly attributed to the structure variations within the nanocrystals. The phonons below 30 meV in silicon nanocrystals show temperature dependence opposite to the bulk silicon, explained by the large anharmonicity of the under-constrained near-surface phonons. This is supported by the abnormal atomic mean-square-displacement, and low energy phonon population in small silicon nanocrystals. This work provides crucial information on the phonon dynamics in spatially confined materials. |
Smith, H L; Li, Chen W; Hoff, A; Garrett, G R; Kim, D S; Yang, F C; Lucas, M S; Swan-Wood, T; Lin, J Y Y; Stone, M B; Abernathy, D L; Demetriou, M D; Fultz, B Separating the configurational and vibrational entropy contributions in metallic glasses Journal Article Nature Physics, 13 (9), pp. 900-905, 2017. Links | BibTeX | Tags: metallic glass, neutron, phase transition, phonon, thermodynamics, vibrational entropy @article{Smith:2017goa, title = {Separating the configurational and vibrational entropy contributions in metallic glasses}, author = {H L Smith and Chen W Li and A Hoff and G R Garrett and D S Kim and F C Yang and M S Lucas and T Swan-Wood and J Y Y Lin and M B Stone and D L Abernathy and M D Demetriou and B Fultz}, url = {http://www.nature.com/doifinder/10.1038/nphys4142}, doi = {10.1038/nphys4142}, year = {2017}, date = {2017-01-01}, journal = {Nature Physics}, volume = {13}, number = {9}, pages = {900-905}, keywords = {metallic glass, neutron, phase transition, phonon, thermodynamics, vibrational entropy}, pubstate = {published}, tppubtype = {article} } |
Shen, Yang ; Li, Chen W; Tang, Xiaoli ; Smith, Hillary L; Fultz, B honon anharmonicity and components of the entropy in palladium and platinum Journal Article Physical Review B, 93 , pp. 214303, 2016. Abstract | Links | BibTeX | Tags: anharmonicity, neutron, phonon, vibrational entropy @article{Shen2016, title = {honon anharmonicity and components of the entropy in palladium and platinum}, author = {Shen, Yang and Li, Chen W. and Tang, Xiaoli and Smith, Hillary L. and Fultz, B.}, url = {https://journals.aps.org/prb/abstract/10.1103/PhysRevB.93.214303}, doi = {10.1103/PhysRevB.93.214303}, year = {2016}, date = {2016-06-07}, journal = {Physical Review B}, volume = {93}, pages = {214303}, abstract = {Inelastic neutron scattering was used to measure the phonon density of states in fcc palladium and platinum metal at temperatures from 7 K to 1576 K. Both phonon-phonon interactions and electron-phonon interactions were calculated by methods based on density functional theory (DFT) and were consistent with the measured shifts and broadenings of phonons with temperature. Unlike the longitudinal modes, the characteristic transverse modes had a nonlinear dependence on temperature owing to the requirement for a population of thermal phonons for upscattering. Kohn anomalies were observed in the measurements at low temperature and were reproduced by calculations based on DFT. Contributions to the entropy from phonons and electrons were assessed and summed to obtain excellent agreement with prior calorimetric data. The entropy from thermal expansion is positive for both phonons and electrons but larger for phonons. The anharmonic phonon entropy is negative in Pt, but in Pd it changes from positive to negative with increasing temperature. Owing to the position of the Fermi level on the electronic DOS, the electronic entropy was sensitive to the adiabatic electron-phonon interaction in both Pd and Pt. The adiabatic EPI depended strongly on thermal atom displacements.}, keywords = {anharmonicity, neutron, phonon, vibrational entropy}, pubstate = {published}, tppubtype = {article} } Inelastic neutron scattering was used to measure the phonon density of states in fcc palladium and platinum metal at temperatures from 7 K to 1576 K. Both phonon-phonon interactions and electron-phonon interactions were calculated by methods based on density functional theory (DFT) and were consistent with the measured shifts and broadenings of phonons with temperature. Unlike the longitudinal modes, the characteristic transverse modes had a nonlinear dependence on temperature owing to the requirement for a population of thermal phonons for upscattering. Kohn anomalies were observed in the measurements at low temperature and were reproduced by calculations based on DFT. Contributions to the entropy from phonons and electrons were assessed and summed to obtain excellent agreement with prior calorimetric data. The entropy from thermal expansion is positive for both phonons and electrons but larger for phonons. The anharmonic phonon entropy is negative in Pt, but in Pd it changes from positive to negative with increasing temperature. Owing to the position of the Fermi level on the electronic DOS, the electronic entropy was sensitive to the adiabatic electron-phonon interaction in both Pd and Pt. The adiabatic EPI depended strongly on thermal atom displacements. |
Bansal, D; Hong, J; Li, Chen W; May, A F; Porter, W; Hu, M Y; Abernathy, D L; Delaire, O Phonon anharmonicity and negative thermal expansion in SnSe Journal Article Physical Review B, 94 (5), pp. 054307, 2016. Links | BibTeX | Tags: neutron, NTE, phonon, selenide, thermodynamics, thermoelectric @article{Bansal:2016hd, title = {Phonon anharmonicity and negative thermal expansion in SnSe}, author = {D Bansal and J Hong and Chen W Li and A F May and W Porter and M Y Hu and D L Abernathy and O Delaire}, url = {https://link.aps.org/doi/10.1103/PhysRevB.94.054307}, doi = {10.1103/PhysRevB.94.054307}, year = {2016}, date = {2016-01-01}, journal = {Physical Review B}, volume = {94}, number = {5}, pages = {054307}, keywords = {neutron, NTE, phonon, selenide, thermodynamics, thermoelectric}, pubstate = {published}, tppubtype = {article} } |
Li, Chen W; Hong, J; May, A F; Bansal, D; Chi, S; Hong, T; Ehlers, G; Delaire, O Orbitally driven giant phonon anharmonicity in~SnSe Journal Article Nature Physics, 11 (12), pp. 1063–1069, 2015. Links | BibTeX | Tags: anharmonicity, neutron, selenide, thermoelectric @article{Li:2015gf, title = {Orbitally driven giant phonon anharmonicity in~SnSe}, author = {Chen W Li and J Hong and A F May and D Bansal and S Chi and T Hong and G Ehlers and O Delaire}, url = {http://www.nature.com/doifinder/10.1038/nphys3492}, doi = {10.1038/nphys3492}, year = {2015}, date = {2015-01-01}, journal = {Nature Physics}, volume = {11}, number = {12}, pages = {1063--1069}, keywords = {anharmonicity, neutron, selenide, thermoelectric}, pubstate = {published}, tppubtype = {article} } |
Budai, J D; Hong, J; Manley, M E; Specht, E D; Li, Chen W; Tischler, J Z; Abernathy, D L; Said, A H; Leu, B M; Boatner, L A; McQueeney, R J; Delaire, O Metallization of vanadium dioxide driven by large phonon entropy Journal Article Nature, 515 (7528), pp. 535-539, 2014. Links | BibTeX | Tags: anharmonicity, metal-insulator transition, neutron, phonon, synchrotron, thermodynamics, vibrational entropy @article{budai_metallization_2014, title = {Metallization of vanadium dioxide driven by large phonon entropy}, author = {J D Budai and J Hong and M E Manley and E D Specht and Chen W Li and J Z Tischler and D L Abernathy and A H Said and B M Leu and L A Boatner and R J McQueeney and O Delaire}, url = {http://www.nature.com/doifinder/10.1038/nature13865}, doi = {10.1038/nature13865}, year = {2014}, date = {2014-11-01}, journal = {Nature}, volume = {515}, number = {7528}, pages = {535-539}, keywords = {anharmonicity, metal-insulator transition, neutron, phonon, synchrotron, thermodynamics, vibrational entropy}, pubstate = {published}, tppubtype = {article} } |
Lan, T; Li, Chen W; Niedziela, J L; Smith, H L; Abernathy, D L; Rossman, G R; Fultz, B Anharmonic lattice dynamics of Ag2O studied by inelastic neutron scattering and first-principles molecular dynamics simulations Journal Article Physical Review B, 89 (5), pp. 2022, 2014. Links | BibTeX | Tags: anharmonicity, neutron, oxide, phonon @article{lan_anharmonic_2014, title = {Anharmonic lattice dynamics of Ag2O studied by inelastic neutron scattering and first-principles molecular dynamics simulations}, author = {T Lan and Chen W Li and J L Niedziela and H L Smith and D L Abernathy and G R Rossman and B Fultz}, url = {https://link.aps.org/doi/10.1103/PhysRevB.89.054306}, doi = {10.1103/PhysRevB.89.054306}, year = {2014}, date = {2014-01-01}, journal = {Physical Review B}, volume = {89}, number = {5}, pages = {2022}, keywords = {anharmonicity, neutron, oxide, phonon}, pubstate = {published}, tppubtype = {article} } |
Li, Chen W; Ma, J; Cao, H B; May, A F; Abernathy, D L; Ehlers, G; Hoffmann, C; Wang, X; Hong, T; Huq, A; Gourdon, O; Delaire, O Anharmonicity and atomic distribution of SnTe and PbTe thermoelectrics Journal Article Physical Review B, 90 (21), pp. 194, 2014. Links | BibTeX | Tags: anharmonicity, lattice dynamics, neutron, phonon, telluride @article{li_anharmonicity_2014, title = {Anharmonicity and atomic distribution of SnTe and PbTe thermoelectrics}, author = {Chen W Li and J Ma and H B Cao and A F May and D L Abernathy and G Ehlers and C Hoffmann and X Wang and T Hong and A Huq and O Gourdon and O Delaire}, url = {https://link.aps.org/doi/10.1103/PhysRevB.90.214303}, doi = {10.1103/PhysRevB.90.214303}, year = {2014}, date = {2014-01-01}, journal = {Physical Review B}, volume = {90}, number = {21}, pages = {194}, keywords = {anharmonicity, lattice dynamics, neutron, phonon, telluride}, pubstate = {published}, tppubtype = {article} } |
Li, Chen W; Hellman, O; Ma, J; May, A F; Cao, H B; Chen, X; Christianson, A D; Ehlers, G; Singh, D J; Sales, B C; Delaire, O Phonon Self-Energy and Origin of Anomalous Neutron Scattering Spectra in SnTe and PbTe Thermoelectrics Journal Article Physical Review Letters, 112 (17), pp. 194, 2014. Links | BibTeX | Tags: anharmonicity, neutron, phonon, thermoelectric @article{li_phonon_2014, title = {Phonon Self-Energy and Origin of Anomalous Neutron Scattering Spectra in SnTe and PbTe Thermoelectrics}, author = {Chen W Li and O Hellman and J Ma and A F May and H B Cao and X Chen and A D Christianson and G Ehlers and D J Singh and B C Sales and O Delaire}, url = {https://link.aps.org/doi/10.1103/PhysRevLett.112.175501}, doi = {10.1103/PhysRevLett.112.175501}, year = {2014}, date = {2014-01-01}, journal = {Physical Review Letters}, volume = {112}, number = {17}, pages = {194}, keywords = {anharmonicity, neutron, phonon, thermoelectric}, pubstate = {published}, tppubtype = {article} } |
Munoz, J A; Lucas, M S; Delaire, O; Winterrose, M L; Mauger, L; Li, Chen W; Sheets, A O; Stone, M B; Abernathy, D L; Xiao, Y; Chow, P; Fultz, B Positive Vibrational Entropy of Chemical Ordering in FeV Journal Article Physical Review Letters, 107 (11), pp. 115501, 2011. Links | BibTeX | Tags: Fe, neutron, synchrotron, vibrational entropy @article{munoz_positive_2011, title = {Positive Vibrational Entropy of Chemical Ordering in FeV}, author = {J A Munoz and M S Lucas and O Delaire and M L Winterrose and L Mauger and Chen W Li and A O Sheets and M B Stone and D L Abernathy and Y Xiao and P Chow and B Fultz}, url = {https://link.aps.org/doi/10.1103/PhysRevLett.107.115501}, doi = {10.1103/PhysRevLett.107.115501}, year = {2011}, date = {2011-09-01}, journal = {Physical Review Letters}, volume = {107}, number = {11}, pages = {115501}, keywords = {Fe, neutron, synchrotron, vibrational entropy}, pubstate = {published}, tppubtype = {article} } |
