Skip to Main Content

The University of Tennessee


Frequently Used Tools:

Materials Structure Interactive Gallery

Main Navigation:

Effect of temperature on lattice parameter and bulk modulus of mixed Uranium-Thorium oxides

Matthew Loyd
Department of Materials Science & Engineering, University of Tennessee

This page shows visualizations of the a UO2 lattice that has been displaced so that the resulting stresses can be used to calculate the bulk modulus. This was done using a modified version of the ELASTIC_T example for the 2018 spring course MSE 614.

Understanding the mechanical properties of actinide oxides at different temperatures has many implications in planning fuel cells and handling spent nuclear fuel. In this work, I investigated a composition that has important in mixed oxide (MOX) fuel cycles, UxTh1-xO2. To do this, I used the EAM potential for this composition [1], and built my own LAMMPS input files. I determined the lattice parameter for UO2, ThO2, and 3 intermediate compositions from 300-1000 K and at 0 GPa pressure. The average linear coefficientof thermal expansion for each composition is included in the table blow

Composition Thermal Expansion (x 106 K-1)
UO2 6.40
U3ThO8 6.12
UThO4 7.02
UTh3O8 5.83
ThO2 6.68

Next, I used a LAMMPS example that perturbs the simulated atoms and measures resultant stress to calculate the bulk modulus at the same temperatures and pressure. This is simulatied below.

Interactive Structures

Color Legend:

  • Blue = Uranium
  • Green = Thorium
  • Red = Oxygen


[1] Atomistic Simulation Group, Library of Potentials, Online, October 2015,

posted: April 2018.
updated: April 2018.