Volumen II - SAM

Figure 2. Minimum energy 3I configuration (a), and mobile 4I for ED (b) and EAM (c).
Regarding the static simulations, details on 1I have been given in [20]. The most important features are: i)
for both models the easiest jump occurs to a nearest neighbor with reorientation of the dumbbell axis, and ii)
only structures are relevant for ED, whereas structures appear for EAM by on-site rotation or
translation from . The obtained E m values are 0.62 eV / 0.60 eV for EAM / ED.
For the remaining clusters, visual inspection of the sequences turns out to be very cumbersome, thus
complicating the analysis. This stems from the numerous detected saddles that amount to small SIA
rearrangements or oscillations within the cluster, leading to no migration as a whole. Clearly, these effects
are rooted in the rather independent behavior of individual SIAs mentioned earlier. A global approach,
capable of revealing the most salient features, is needed. Thus, two basic techniques were employed; the
chain of local minima and connecting saddles was partitioned in sub-chains according to the lowest energy
structure, keeping only those whose end points were spatially separated in more than a certain threshold
distance. For each sub-chain, the maximum energy saddle was determined, and then the least of all those
values chosen as candidate for overall energy barrier. The latter assertion, however, must be confirmed by
visual inspection, because the associated transition state need not correspond to RCM translation (though
generally it does). A complementary approach consists in ordering all the saddles according to increasing
energy and single out (some of) those connecting to the lowest energy structure, which is how the tables
below have been constructed.
Table 1. Migration mechanisms and barriers for the 2I cluster and both potentials
EAM
Transition E m (eV)
ED
Transition E m (eV)
D1 → D3 0.42 D1 → D2* 0.39
D1 → D2 0.52 D1 → D3 0.42
D1 → D3* 0.53 D1 → D2 0.55
D1 → D1* 0.60
D1 → C1
0.65
Figure 3. Optimum jump mechanisms for the 2I cluster
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