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We have calculated the electrostatic interaction between two
rod-like charged objects with arbitrary orientations in three
dimensions. We obtained a closed-form formula expressing the
interaction energy in terms of the separation distance between the
centers of the two rod-like objects, r, their lengths $(denoted by
2\frac{l}{}1 and 2\frac{l}{}2)$ and their relative orientations
(indicated by $\theta$ and $\phi$). When the objects have the same
length $(2\frac{l}{}1 = 2\frac{l}{}2 = l)$, for particular values of
separations, i.e. for $r \preceq 0.8l$, two types of minimum appear
in the interaction energy with respect to $\theta$. By employing the
closed-form formula and introducing a scaled temperature t, we have
also studied the thermodynamic properties of a 1D system of rod-like
charged objects. For different separation distances, the dependence
of the specific heat of the system to the scaled temperature has
been studied. It is found that, for r < 0.8l, the specific heat has
a maximum.
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