Defect Arrhenius: c(E_f=0)=1; c(E_f=k_B·T)=exp(-1)

Sympy-exact witness of the Arrhenius defect-concentration limiting cases. Setup: c = exp(-E_f/(T·k_B)). Identity 1 (zero formation energy, E_f=0): c = exp(0) = 1 — every site is vacant, the trivial upper bound (all-sites-vacant, clearly…