Calculation of free energy of Al-Li-Mg alloy by TF equation

Based on the TF (Thomas-Fermi) equation, the interior potential boundary condition under the electric field was established. Free energies were calculated under the influence of electric field with the defined boundary for the single atom, solid solution, compound and practical alloys. It can be concluded that the monatomic free energy under the electric field was not symmetrical about zero point of the external potential. The free energy sensitivities of the three calculated elements on the side of positive electric field take turns of Al, Li, and Mg, and take turns of Al, Mg and Li on the side of negative electric field. The free energies of Al₃Li compound and Al-2.14%Li solid solution exhibit different electric field symmetries and sensitivities in the electric field, and the Al-2.14%Li is more sensitive than the Al₃Li at 460 K and 800 K. The free energy of solid solution Al-2.14%Li is higher than the compound Al₃Li at 800 K under higher electric field, the free energy of Al₃Li is lower than Al-2.14%Li at 460 K. The free energy of 1420 alloy is symmetrical about the zero external potential, consistent with its tensile properties during aging process in the electric-field.