Abstract Scope |
Machine-learnt interatomic potentials such as MTPs (Shapeev, 2016) trained to high-temperature DFT data predict energies and forces of atomic configurations highly accurately. In combination with thermodynamic integration (TUTILD, Duff, 2015), one can calculate total free energies of HEAs to 1 meV accuracy (Grabowski, 2019, Ferrari, 2020) up to melting point, including vibrational contributions with anharmonicity. We demonstrate this for various refractory BCCs ranging from unaries to five-component HEAs and break-down the total free energies to individual contributions. Certain BCC unaries have a small positive anharmonic contribution (beyond quasi-harmonic) whereas the others have a large negative anharmonicity, which is also reflected in the HEAs that constitute them. This is in contrast to FCCs (Glensk, 2015) where there is always a positively increasing contribution with temperature. We narrow this feature to DOS and first- and second neighbor forces and illustrate differences in bonding behavior in different BCCs. |