A supercell containing 91 atoms was used (13 Be, 26 Li, and 52 F). The simulation cell volume was imposed based on the FLiBe density of 2.0314 g/mL and 1.937 g/mL at 510 °C and 700 °C, respectively. Assuming natural isotopics for Li of 92.5% and 6.94 g/mol Li atomic weight, the cell lengths are 10.17 Å and 10.33 Å, respectively. Recent experiments found the density of FLiBe to be 2.029(11) g/mL and 1.948 (14) g/mL at 510 °C and 700 °C, respectively, with a molecular weight of 33.02(5) g/mol, LiF/BeF 2 molar ratio of 1.977, and 93.12% Li enrichment. The supercell was first initialized with a random structure generated with the Packmol package to avoid overlapping atomic positions. The initial random configuration was equilibrated at 510 °C and 700 °C for 20 ps to develop the liquid structure. Once equilibrated, nearly 50 ps simulation trajectory should be sufficent to obtain converged molten-salt structure and properties according to our previous work. A time step of 2 fs was used for all AIMD simulations. The pressure of the equilibrated fixed-volume cells was -500 and -300 MPa, respectively (95% confidence interval).