Extensible freely jointed chain
= Extensible freely jointed chain
{title2=$z=L\mathcal L(fb/(k_BT))+Lf/S$}
A <freely jointed chain> supplemented with axial segment compliance. A simple phenomenological additive law is $z=L\mathcal L(fb/(k_BT))+Lf/S$, where $L=Nb$, $\mathcal L$ is the <Langevin function> and $S$ is an axial stretch modulus with units of force. This adds energetic compliance to the <entropic spring>; it is not an exact angular average for arbitrary harmonic-link statistics.