Figure 1.

Simulated nanoporous gold. The simulation model was as follows: a bond-breaking model was used for diffusion; atoms with N nearest neighbors diffused with rate $k_N=v_D\text{exp}(-(N_{\mathrm{ϵ}}/k_{B}T)$, where e is a bond energy and v_{D = 10}¹³ _s⁻¹. Dissolution rates were consistent with the Butler-Volmer (BV) equation in the high-driving-force Tafel regime; the dissolution rate k_E,N for a silver atom with N nearest neighbors was written as $k_{E,N}=v_E\text{exp}[-(N_{\mathrm{ϵ}}-\mathrm{\varphi }/k_{B}T)$, where v_E = 10⁴ s⁻¹ is an attempt frequency determined by the exchange-current density in the BV equation and φ is the over-potential. For the Figure, φ = 1.75 eV, ϵ/k_BT = 5.51. Reprinted with permission from [39]. Copyright 2001, Nature Publishing Group.