Relative stability of the various phases of aluminum as computed by DFT and ReaxFF.
Bond dissociation profile of dimer as computed by DFT and ReaxFF. The energies were computed with reference to the equilibrium bond length’s energy.
Small representative isomers of , , and clusters as predicted by DFT and ReaxFF. DFT predicts that structures a, c, and f are the most stable configurations for , , and , respectively. ReaxFF, on the other hand, predicts that structures b, d, and g are the most stable configurations for , , and , respectively.
Heating up of at a rate of .
Simulated tempering of cluster.
Stability function as a function of cluster size. The peaks in the figure show the most stable clusters based on geometric considerations. Positive values of stability function indicate that the cluster is stable.
Some of the magic clusters of aluminum, , , , , , and , predicted by ReaxFF.
Binding energy per atom for aluminum clusters with as a function of cluster size .
(a) Variation in potential energy with time during the heating process of aluminum slab with 500 atoms. (b) Potential energy and heat capacity for heating and cooling cycle of aluminum slab with 500 atoms. (c) The Lindemann index for heating aluminum slab with 500 atoms. (d) The RDFs of the initial starting structure at 300 K and the cooled structure at 300 K. From the RDFs, the starting structure is crystalline but the cooled structure is in an amorphous state (indicated by a split in the second peak).
(a) Variation in potential energy with time during the heating process of aluminum cluster with 1024 atoms. The starting structure is amorphous. At about 170 ps (700 K) the system finds a more stable configuration, which is crystalline. (b) Potential energy and heat capacity for heating-cooling cycle of aluminum cluster with 1024 atoms. When cooled, the system goes to a crystalline state.
The radial distribution functions of the heated and cooled conformations of aluminum cluster with 1024 atoms, as shown in Fig. 10.
The potential energy and heat capacity for heating-cooling cycle of aluminum cluster with 1024 atoms starting with different configurations.
(i) Variation in energy with time during heating of . The temperature was ramped up at a rate of . (ii) Radial distribution functions of structures (a), (b), and starting structure (start).
(i) The heating curve, at a heating rate of , for structure (b) in Fig. 13 (i). (ii) Radial distribution functions of structures (a), (b), (c), (d), and (e) formed during the heating process.
Schematic representation of the structural evolution of a cluster with increase in temperature.
The relative number of bonded pairs, 1421, 1422, 1551, and 1431 for the two conformations of clusters (a) and (b), as shown in Fig. 13 (i).
HA pairs for during the cooling process from 700 to 0 K.
Geometries of .
Radial distribution function of the amorphous and crystalline states of cluster.
Bond energy and bond-order parameters. is in kcal/mol.
van der Waals parameters and bond radius parameters.
Average interatomic distance (in angstrom) of small clusters used in the training set. means the average distance from the atom in the center of the icosahedral to that on the surface.
Melting point of and bulk aluminum as computed by various potentials (Ref. 60) and ReaxFF. The given values for ReaxFF were those determined from a heating rate of .
Cohesive energies (in kcal/mol per atom) for some aluminum clusters.
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