Study On The Atomistic Simulation For Excess Stored Energy Of Aluminm Nanoparticles

Aluminum (Al) nanoparticles have been of considerable fundamental and appliedinterest in recent years as metallic fuel for propulsion systems due to their high energydensity and high specific surface area that cannot be obtained in the conventionalmicron-sized Al particles. In this paper, on the basis of the early experimental research ofour group, molecular dynamics simulations based on the modified analytical embeddedatom method (MAEAM) potentials were employed to quantitatively analyze the excessstored energy respectively produced by size effect and non-size effect of Alnanoparticles.Firstly, molecular dynamics simulations based on MAEAM potentials was used tostudy the excess stored energy of bulk Al with different vacancy concentrations in thetemperature of300K, we found that with the gradual increase in the vacancy concentration,the lattice parameter, total energy of the system, excess stored energy and average vacancyformation energy approximately varied linearly.Molecular dynamics simulations based on MAEAM potentials was used to study thevariation of excess stored energy and related parameters produced by size effect of Alnanoparticles (particle size ranges of0.6-22nm) at zero temperature, finding that the latticeparameter, lattice contraction, cohesive energy, excess stored energy and surface energy ofAl nanoparticles are size dependent; gradually decreases with the particle size the excessstored energy ranges from2.12to57.61kJ/mol, which is in the same order of magnitudewith experimental measurements; as the size of Al nanoparticles decreases gradually, thecalculated surface energy of Al nanoparticles to be in the range of0.78-1.10J/m2, whichis quite close to the results calculated by other simulation methods.In addition, we findthat non-uniform lattice distortion exists in Al nanoparticles, and non-uniform latticedistortion mainly concentrates in the first or second shell of the surface layers. Molecular dynamics simulations based on MAEAM potentials was used to study thevariation of excess stored energy and related parameters produced by non-size effect of Alnanoparticles at a given size (of10nm in diameter) at zero temperature. From thesimulation results, with the gradual increase in the vacancy concentration, the latticeparameter, lattice contraction and excess stored energy of Al nanoparticles vary linearly.When the vacancy concentration of Al nanoparticles increases from0%to3%, thesimulated excess stored energy increases from4.68kJ/mol to7.21kJ/mol, which is quiteclose to the experimental results. One to one relationship among vacancy concentration,lattice contraction and excess stored energy of Al nanoparticles at a given size gives ussome enlightenment, through the experimental determination of size and latticecontraction of metallic nanoparticles, the corresponding vacancy concentration and excessstored energy can be predicted by MAEAM approach.