= Polymer overlap volume fraction
{title2=$\phi^*\sim Nv_0/R^3$}
The <polymer overlap volume fraction> counts the segment <volume> of one chain divided by its coil <volume>. If the segment <volume> is $v_0$ and $R\sim bN^\nu$, then $\phi^*\sim(v_0/b^3)N^{1-3\nu}$. The site-volume convention $v_0\sim b^3$ gives $N^{-4/5}$ for the three-dimensional <Flory approximation> and $N^{-1/2}$ for an <ideal chain>. A geometric coil <volume> such as $4\pi R_g^3/3$ changes a prefactor; segment <length> and segment <volume> are not generally interchangeable without a model convention.
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