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-The basic idea is that, in real systems, the bond order depends upon the local environment.
-An atom with many neighbors forms weaker bonds than an atom with few neighbors since .
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-Here comes an explanation, energy per bond monotonically decreasing with the amount of bonds and so on and so on \ldots
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+The basic idea is that, in real systems, the bond order, i.e. the strength of the bond, depends upon the local environment \cite{abell85}.
+Atoms with many neighbors form weaker bonds than atoms with only a few neighbors.
+Although the bond strength intricately depends on geometry the focus on coordination, i.e. the number of neighbors forming bonds, is well motivated qualitatively from basic chemistry since for every additional formed bond the amount of electron pairs per bond and, thus, the strength of the bonds is decreased.
+If the energy per bond decreases rapidly enough with increasing coordination the most stable structure will be the dimer.
+In the other extreme, if the dependence is weak, the material system will end up in a close-packed structure in order to maximize the number of bonds and likewise minimize the cohesive energy.
+This suggests the bond order to be a monotonously decreasing function with respect to coordination and the equilibrium coordination being determined by the balance of bond strength and number of bonds.
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+Tersoff incorporated the concept of bond order based on pseudopotential theory \cite{abell85} in a three-body potential formalism.