Fig. 4: The change of the total energy with respect to the initial state, as a function of the distance travelled by the C-interstitial when a (C–Si)Si split-interstitial approaches a CSi substitutional.
From: The kinetics of carbon pair formation in silicon prohibits reaching thermal equilibrium

The curves are cubic spline fits, to guide the eye. a The formation of the neutral (red curve) and positive (blue curve) A-configuration. b The formation of the neutral C-configuration.