= Dissipation potential
{title2=$\dot\xi_r=\partial\Omega/\partial f_r$}
A <dissipation potential> is a function used to generate dissipative rates or their conjugate driving forces. In a force-based convention, a potential $\Phi(X)$ specifies an <internal variable> rate through $\dot\alpha=\partial_X\Phi$. For example, $\Phi=X^2/(2\eta)$ with $\eta>0$ gives $\dot\alpha=X/\eta$ and dissipation $X\dot\alpha=X^2/\eta\geq0$.
If $\Phi$ is differentiable and convex with a minimum at $X=0$, the convexity inequality gives $X\partial_X\Phi\geq\Phi(X)-\Phi(0)\geq0$. This supplies a direct route to nonnegative dissipation. A rate-based convention instead generates forces from rates, so its variables must be stated explicitly. The potential is useful for organizing <constitutive equations>, but the complete model must still satisfy the <Clausius-Duhem inequality>, including thermal terms and the chosen energetic sign convention.
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