Effect of voids and pressure on melting of nano-particulate and bulk aluminum |
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Authors: | Puneesh Puri Vigor Yang |
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Institution: | (1) The Pennsylvania State University, University Park, PA 16802, USA |
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Abstract: | Molecular dynamics simulations are performed using isobaric–isoenthalpic (NPH) ensembles to study the effect of internal defects
in the form of voids on the melting of bulk and nano-particulate aluminum in the size range of 2–9 nm. The main objectives
are to determine the critical interfacial area required to overcome the free energy barrier for the thermodynamic phase transition,
and to explore the underlying mechanisms for defect-nucleated melting. The inter-atomic interactions are captured using the
Glue potential, which has been validated against the melting temperature and elastic constants for bulk aluminum. A combination
of structural and thermodynamic parameters, such as the potential energy, Lindemann index, translational-order parameter,
and radial-distribution functions, are employed to characterize the melting process. The study considers a variety of void
shapes and sizes, and results are compared with perfect crystals. For nano aluminum particles smaller than 9 nm, the melting
temperature is size dependent. The presence of voids does not impact the melting properties due to the dominancy of nucleation
at the surface, unless the void size exceeds a critical value beyond which lattice collapse occurs. The critical void size
depends on the particle dimension. The effect of pressure on the particulate melting is found to be insignificant in the range
of 1–300 atm. The melting behavior of bulk aluminum is also examined as a benchmark. The critical interfacial area required
for the solid–liquid phase transition is obtained as a function of the number of atoms considered in the simulation. Imperfections
such as voids reduce the melting point. The ratio between the structural and thermodynamic melting points is 1.32. This value
is comparable to the ratio of 1.23 for metals like copper. |
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Keywords: | Aluminum Voids Nanoparticles Melting Molecular dynamics Modeling and simulation |
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