  A physically defined QCD coupling parameter naturally incorporates massive
quark flavor thresholds in a gauge invariant, renormalization scale independent
and analytical way. In this paper we summarize recent results for the
finite-mass fermionic corrections to the heavy quark potential through two
loops leading to the numerical solution of the physical and mass dependent
Gell-Mann Low function. The decoupling-, massless- and Abelian-limits are
reproduced and an analytical fitting function is obtained in the V-scheme. Thus
the gauge invariant mass dependence of $\alpha_V$ is now known through two
loops. Possible applications in lattice analyses, heavy quark physics and
effective charges are briefly discussed.
