Bulk properties -The phase diagram for Li-Na systems shows a large immiscibility in the two metals' liquid and solid-state at standard conditions 107 . Instead, a eutectic alloy is formed where both alloy components maintain their crystal structures, and the alloy behaves neither as a solid solution nor as an intermetallic particle 105 . Hence, we generated different theoretical Li-Na alloy bulk phases with different compositions for the force field training of the Li-Na interaction to include a broad range of different binding structures. Apart from the lattice constants and angles, the bulk modulus of the respective phase was calculated by compressing and expanding the lattice. Further, the energy of formation per formula unit ∆ f E referenced to the bcc bulk phases of lithium and sodium was determined by