Green-Kubo Diffusion

D = ∫₀^∞ ⟨v(0)·v(t)⟩dt — velocity autocorrelation → diffusion coefficient

Langevin equation:
mẍ = −γmẋ + √(2γmkT)·ξ(t)

VACF: C(t) = ⟨v(0)·v(t)⟩
C(t) = (kT/m)·e^(−γt)

Green-Kubo:
D = ∫₀^∞ C(t)/1 dt = kT/γm

Einstein relation:
D = kT/(γm)
(fluctuation-dissipation)

D_GK = D_Einstein ✓
Both → same value!
Computing...