My research goals for this summer was to better learn VASP and to test different density functionals using VASP on typical ferroelectric materials (barium titanate (BTO) and lead titanate (PTO)) in the hopes of finding an alternative to the commonly used functions which over- or underestimate certain properties of the material with respect to experimental results. We started off looking into a particular functional MN15-L which didn't seem to yield better results than LDA or PBE functionals. Thus, we decided to look into the other Minnesota functionals which also appeared promising due to their results for molecules and atoms, but haven't yet been tested on ferroelectric materials. I also wanted to look at the distortion path from the cubic (non-polar and high energy) structure to the tetragonal (polar and low energy) structure to see the evolution of certain material properties. Specifically, I wanted to look at the evolution of the polarization and free energy along the distortion path. I also looked at the band gap energy of the tetragonal state since computationally cheap functionals don't estimate this well.
As far as what I've accomplished, I've run all but three of the Minnesota functionals on BTO. The three that haven't been run are computationally expensive and the one has run for multiple days and not finished more than one step in the distortion path which seems computationally prohibitive for such a short time for research on this project. I've also run PTO for half of the functionals, but due to finding an error in my input file, I haven't been able to obtain the corrected results for this material at this time. Most of the time spent went to waiting for simulations in the queue and to run, and debugging my input files. I feel that once I've completed the results for PTO and finished running those other 3 for BTO, then we might have a publishable paper.