Improving the function for grain boundary energy interpolation in uranium dioxide

Others have made efforts to find an interpolation function for the grain boundary
(GB) energies of uranium dioxide, based on work done by Bulatov et al.[Acta Mater.
65, 161 (2014)]. This work developed a MATLAB® script based on Harbison[B.S.
Thesis, Brigham Young University - Idaho (2015)] and Bulatov et al. to improve
such a function. This work collected molecular dynamics data using the LAMMPS
(Large-scale Atomic/Molecular Massively Parallel Simulation) program developed at
Sandia National Laboratory. This work collected results for the 〈100〉, 〈110〉, and
〈111〉 symmetric tilt and twist GBs. Calculating the new data with an 800 K anneal
allowed the atoms to relax to a lower energy state. The 〈100〉 and 〈110〉 symmetric
tilt and 〈110〉 twist sets show an improved fit, whereas the 〈100〉 twist and 〈111〉
symmetric tilt and twist sets show unexpected trends. Further research needs to be
done for the 〈100〉 and 〈111〉 sets to determine why the fitting procedure does not
accurately reflect the expected results. Additional research should also be done to
determine if outlying data points necessitate fitting additional cusps.