Kim, D. S.; Hellman, O.; Herriman, J.; Smith, H. L.; Lin, J. Y. Y.; Shulumba, N.; Niedziela, J. L.; Li, C. W.; Abernathy, D. L.; Fultz, B.
Nuclear quantum effect with pure anharmonicity and the anomalous thermal expansion of silicon Journal Article
In: Proceedings of the National Academy of Sciences, vol. 115, no. 9, pp. 1992, 2018.
Abstract | Links | BibTeX | Tags: anharmonicity, first-principles, high temperature, lattice expansion
@article{Kim2018,
title = {Nuclear quantum effect with pure anharmonicity and the anomalous thermal expansion of silicon},
author = {D. S. Kim and O. Hellman and J. Herriman and H. L. Smith and J. Y. Y. Lin and N. Shulumba and J. L. Niedziela and C. W. Li and D. L. Abernathy and B. Fultz},
url = {https://www.pnas.org/content/115/9/1992},
doi = {10.1073/pnas.1707745115},
year = {2018},
date = {2018-02-27},
journal = {Proceedings of the National Academy of Sciences},
volume = {115},
number = {9},
pages = {1992},
abstract = {Despite the widespread use of silicon in modern technology, its peculiar thermal expansion is not well understood. Adapt- ing harmonic phonons to the specific volume at temperature, the quasiharmonic approximation, has become accepted for sim- ulating the thermal expansion, but has given ambiguous inter- pretations for microscopic mechanisms. To test atomistic mech- anisms, we performed inelastic neutron scattering experiments from 100 K to 1,500 K on a single crystal of silicon to mea- sure the changes in phonon frequencies. Our state-of-the-art ab initio calculations, which fully account for phonon anharmonic- ity and nuclear quantum effects, reproduced the measured shifts of individual phonons with temperature, whereas quasiharmonic shifts were mostly of the wrong sign. Surprisingly, the accepted quasiharmonic model was found to predict the thermal expan- sion owing to a large cancellation of contributions from individual phonons.},
keywords = {anharmonicity, first-principles, high temperature, lattice expansion},
pubstate = {published},
tppubtype = {article}
}
Despite the widespread use of silicon in modern technology, its peculiar thermal expansion is not well understood. Adapt- ing harmonic phonons to the specific volume at temperature, the quasiharmonic approximation, has become accepted for sim- ulating the thermal expansion, but has given ambiguous inter- pretations for microscopic mechanisms. To test atomistic mech- anisms, we performed inelastic neutron scattering experiments from 100 K to 1,500 K on a single crystal of silicon to mea- sure the changes in phonon frequencies. Our state-of-the-art ab initio calculations, which fully account for phonon anharmonic- ity and nuclear quantum effects, reproduced the measured shifts of individual phonons with temperature, whereas quasiharmonic shifts were mostly of the wrong sign. Surprisingly, the accepted quasiharmonic model was found to predict the thermal expan- sion owing to a large cancellation of contributions from individual phonons.
Lan, T; Li, Chen W; Fultz, B
In: Physical Review B, vol. 86, no. 13, pp. 134302, 2012.
Abstract | Links | BibTeX | Tags: anharmonicity, first-principles, phonon, Raman
@article{lan_phonon_2012,
title = {Phonon anharmonicity of rutile SnO 2studied by Raman spectrometry and first principles calculations of the kinematics of phonon-phonon interactions},
author = {T Lan and Chen W Li and B Fultz},
url = {https://link.aps.org/doi/10.1103/PhysRevB.86.134302},
doi = {10.1103/PhysRevB.86.134302},
year = {2012},
date = {2012-10-01},
journal = {Physical Review B},
volume = {86},
number = {13},
pages = {134302},
abstract = {Raman spectra of rutile tin dioxide (SnO$_2$) were measured at temperatures from 83 to 873 K. The pure anharmonicity from phonon-phonon interactions was found to be large and comparable to the quasiharmonicity. First-principles calculations of phonon dispersions were used to assess the kinematics of three-phonon and four-phonon processes. These kinematics were used to generate Raman peak widths and shifts, which were fit to measured data to obtain the cubic and quartic components of the anharmonicity for each Raman mode. The $B_2g$ mode had a large quartic component, consistent with the symmetry of its atom displacements. The broadening of the $B_2g$ mode with temperature showed an unusual concave-downwards curvature. This curvature is caused by a change with temperature in the number of down-conversion decay channels, originating with the wide band gap in the phonon dispersions.},
keywords = {anharmonicity, first-principles, phonon, Raman},
pubstate = {published},
tppubtype = {article}
}
Raman spectra of rutile tin dioxide (SnO$_2$) were measured at temperatures from 83 to 873 K. The pure anharmonicity from phonon-phonon interactions was found to be large and comparable to the quasiharmonicity. First-principles calculations of phonon dispersions were used to assess the kinematics of three-phonon and four-phonon processes. These kinematics were used to generate Raman peak widths and shifts, which were fit to measured data to obtain the cubic and quartic components of the anharmonicity for each Raman mode. The $B_2g$ mode had a large quartic component, consistent with the symmetry of its atom displacements. The broadening of the $B_2g$ mode with temperature showed an unusual concave-downwards curvature. This curvature is caused by a change with temperature in the number of down-conversion decay channels, originating with the wide band gap in the phonon dispersions.