t06 Small particles are surface
Supplied working report; original verdicts not validated.
Review status: Needs review. This is an archival source note, not a passed proof.
notes.md
# t06 Small particles are surface The posted claim combines two opposing size effects: the exposed-atom fraction grows as 1/d when particles shrink, while the specific activity per surface atom falls for very small particles whose under-coordinated atoms bind intermediates too strongly. Modelling the second term as d^2/(d^2 + d_c^2) gives an activity per unit mass d/(d^2 + d_c^2), which peaks at d = d_c = 1.5 nm and then declines. The interior optimum is therefore reproduced, but only because the second effect was assumed; the test shows the mechanism, not a measurement.