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Electric field along X axes
6e+08
5e+08
4e+08
3e+08
2e+08
1e+08
0
-1e+08
-2e+08
-3e+08
SW-Field = 0
SW-Field = -0.5
SW-Field = +0.5
-4e+08
-5e+08
-1
-0.5
0
0.5
1
X [nm]
Fig. 26. X component of the electric field generated by the bis-ferrocene in different
bias conditions and measured at position of an ideal receiver (Color figure online).
of the receiver and so where the violet lines stand) are subject to an electric
field, whose intensity is almost the same, as well as the direction, but the sign
is opposite and so the result is almost null. This means that the molecule at the
equilibrium does not influence an ideal receiver. For negative applied switching
field (blue curve) the positive peak of the generated electric field moves backward
and it is centered on the receiver. For this reason, the sign of the electric field
that influences the receiver (positive) is opposite with respect to the sign of
the switching field applied to the molecule (negative), thus the receiver should
encode a logic state opposite to the molecule state. On the contrary, in case of
positive switching field (green curve) the situation is dual, since the negative
peak of the generated electric field is centered on the receiver.
3.2
Interaction Between Two Molecules
A complete QCA cell could be implemented aligning two bis-ferrocene molecules
with an ideal inter-molecule distance equal to the width of the molecule. For this
reason, the following step of this analysis concerns the interaction between mole-
cules: the charge distribution of two nearby molecules was evaluated emulating
one of the two molecules with a polarized driver, both in case of neutral and
oxidized bis-ferrocene.
In case of two neutral molecules placed at a distance of 1.0 nm, the dot
charges at the equilibrium are almost zero as reported in Fig. 27 . To model
the effects of a polarized driver the single bis-ferrocene molecule was simulated
in presence of a system of point charges placed at the reference distance from
the molecule. Figure 28 reports the results obtained: considering a neutral bis-
ferrocene molecule (Fig. 28 (A)), the driver was emulated with a positive and a
negative charge to maintain the driver neutrality (Fig. 28 (B)) and the effect on
the target molecule is a slight displacement of charge between the working dots
 
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