# Modeling non-harmonic behavior of materials from experimental inelastic neutron scattering and thermal expansion measurements

## Abstract

Based on thermodynamic principles, we derive expressions quantifying the non-harmonic vibrational behavior of materials, which are rigorous yet easily evaluated from experimentally available data for the thermal expansion coefficient and the phonon density of states. These experimentally-derived quantities are valuable to benchmark first-principles theoretical predictions of harmonic and non-harmonic thermal behaviors using perturbation theory, ab initio molecular-dynamics, or Monte-Carlo simulations. In this study, we illustrate this analysis by computing the harmonic, dilational, and anharmonic contributions to the entropy, internal energy, and free energy of elemental aluminum and the ordered compound FeSi over a wide range of temperature. Our results agree well with previous data in the literature and provide an efficient approach to estimate anharmonic effects in materials.

- Authors:

- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Univ. at Buffalo, NY (United States)
- Duke Univ., Durham, NC (United States)

- Publication Date:

- Research Org.:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

- Sponsoring Org.:
- USDOE Office of Science (SC)

- OSTI Identifier:
- 1311243

- Grant/Contract Number:
- AC05-00OR22725

- Resource Type:
- Journal Article: Accepted Manuscript

- Journal Name:
- Journal of Physics. Condensed Matter

- Additional Journal Information:
- Journal Volume: 28; Journal Issue: 38; Journal ID: ISSN 0953-8984

- Publisher:
- IOP Publishing

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 36 MATERIALS SCIENCE; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; anharmonicity; aluminum; FeSi; free energy; entropy; inelastic neutron scattering; thermal expansion

### Citation Formats

```
Bansal, Dipanshu, Aref, Amjad, Dargush, Gary, and Delaire, Olivier A.
```*Modeling non-harmonic behavior of materials from experimental inelastic neutron scattering and thermal expansion measurements*. United States: N. p., 2016.
Web. doi:10.1088/0953-8984/28/38/385201.

```
Bansal, Dipanshu, Aref, Amjad, Dargush, Gary, & Delaire, Olivier A.
```*Modeling non-harmonic behavior of materials from experimental inelastic neutron scattering and thermal expansion measurements*. United States. doi:10.1088/0953-8984/28/38/385201.

```
Bansal, Dipanshu, Aref, Amjad, Dargush, Gary, and Delaire, Olivier A. Wed .
"Modeling non-harmonic behavior of materials from experimental inelastic neutron scattering and thermal expansion measurements". United States.
doi:10.1088/0953-8984/28/38/385201. https://www.osti.gov/servlets/purl/1311243.
```

```
@article{osti_1311243,
```

title = {Modeling non-harmonic behavior of materials from experimental inelastic neutron scattering and thermal expansion measurements},

author = {Bansal, Dipanshu and Aref, Amjad and Dargush, Gary and Delaire, Olivier A.},

abstractNote = {Based on thermodynamic principles, we derive expressions quantifying the non-harmonic vibrational behavior of materials, which are rigorous yet easily evaluated from experimentally available data for the thermal expansion coefficient and the phonon density of states. These experimentally-derived quantities are valuable to benchmark first-principles theoretical predictions of harmonic and non-harmonic thermal behaviors using perturbation theory, ab initio molecular-dynamics, or Monte-Carlo simulations. In this study, we illustrate this analysis by computing the harmonic, dilational, and anharmonic contributions to the entropy, internal energy, and free energy of elemental aluminum and the ordered compound FeSi over a wide range of temperature. Our results agree well with previous data in the literature and provide an efficient approach to estimate anharmonic effects in materials.},

doi = {10.1088/0953-8984/28/38/385201},

journal = {Journal of Physics. Condensed Matter},

number = 38,

volume = 28,

place = {United States},

year = {Wed Jul 20 00:00:00 EDT 2016},

month = {Wed Jul 20 00:00:00 EDT 2016}

}