# First-principles study of structural, elastic, electronic, vibrational and thermodynamic properties of uranium aluminides

## Abstract

The structural, elastic, electronic, vibrational and thermodynamic properties of uranium aluminides UAl _{x} (x = 2, 3, 4) were studied by density functional theory calculations. The single crystal elastic constants of UAl _{x} were predicted using the stress-strain method, which were further used to calculate the polycrystalline aggregate properties of UAl _{x}, including bulk modulus, shear modulus, Young’s modulus, and Poisson’s ratio, etc. The calculated electronic density of states confirm that UAl _{x} compounds are metallic phases with majority states at the Fermi level contributed by U 5 *f* electrons. The phonon dispersion relations and density of states show that the low frequency acoustic phonon modes of UAl _{x} are dominated by the lattice vibration of uranium atoms while high frequency optical phonon modes are from the vibration of aluminum atoms. Using quasiharmonic approximation, thermodynamic properties of UAl _{x}, including Gibbs free energy, entropy, heat capacity, and linear thermal expansion coefficient, were predicted by including both lattice vibrational and thermal electronic contributions. The thermal electronic energy was found to be crucial for the description of the temperature dependence of the thermodynamic properties. In conclusion, the derived Gibbs energy functions of UAl _{x} are expected to be useful to the thermodynamicmore »

- Authors:

- Argonne National Lab. (ANL), Argonne, IL (United States)

- Publication Date:

- Research Org.:
- Argonne National Lab. (ANL), Argonne, IL (United States)

- Sponsoring Org.:
- USDOE National Nuclear Security Administration (NNSA), Office of Counterterrorism and Counterproliferation

- OSTI Identifier:
- 1483681

- Grant/Contract Number:
- AC02-06CH11357

- Resource Type:
- Journal Article: Accepted Manuscript

- Journal Name:
- Computational Materials Science

- Additional Journal Information:
- Journal Volume: 158; Journal Issue: C; Journal ID: ISSN 0927-0256

- Publisher:
- Elsevier

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 36 MATERIALS SCIENCE; Uranium aluminides; Density function theory calculations; Elastic properties; Thermodynamic properties

### Citation Formats

```
Mei, Zhi -Gang, and Yacout, Abdellatif M.
```*First-principles study of structural, elastic, electronic, vibrational and thermodynamic properties of uranium aluminides*. United States: N. p., 2018.
Web. doi:10.1016/j.commatsci.2018.11.008.

```
Mei, Zhi -Gang, & Yacout, Abdellatif M.
```*First-principles study of structural, elastic, electronic, vibrational and thermodynamic properties of uranium aluminides*. United States. doi:10.1016/j.commatsci.2018.11.008.

```
Mei, Zhi -Gang, and Yacout, Abdellatif M. Wed .
"First-principles study of structural, elastic, electronic, vibrational and thermodynamic properties of uranium aluminides". United States.
doi:10.1016/j.commatsci.2018.11.008.
```

```
@article{osti_1483681,
```

title = {First-principles study of structural, elastic, electronic, vibrational and thermodynamic properties of uranium aluminides},

author = {Mei, Zhi -Gang and Yacout, Abdellatif M.},

abstractNote = {The structural, elastic, electronic, vibrational and thermodynamic properties of uranium aluminides UAlx (x = 2, 3, 4) were studied by density functional theory calculations. The single crystal elastic constants of UAlx were predicted using the stress-strain method, which were further used to calculate the polycrystalline aggregate properties of UAlx, including bulk modulus, shear modulus, Young’s modulus, and Poisson’s ratio, etc. The calculated electronic density of states confirm that UAlx compounds are metallic phases with majority states at the Fermi level contributed by U 5f electrons. The phonon dispersion relations and density of states show that the low frequency acoustic phonon modes of UAlx are dominated by the lattice vibration of uranium atoms while high frequency optical phonon modes are from the vibration of aluminum atoms. Using quasiharmonic approximation, thermodynamic properties of UAlx, including Gibbs free energy, entropy, heat capacity, and linear thermal expansion coefficient, were predicted by including both lattice vibrational and thermal electronic contributions. The thermal electronic energy was found to be crucial for the description of the temperature dependence of the thermodynamic properties. In conclusion, the derived Gibbs energy functions of UAlx are expected to be useful to the thermodynamic modeling of the ternary U-Mo-Al system.},

doi = {10.1016/j.commatsci.2018.11.008},

journal = {Computational Materials Science},

number = C,

volume = 158,

place = {United States},

year = {Wed Nov 14 00:00:00 EST 2018},

month = {Wed Nov 14 00:00:00 EST 2018}

}