Reactive forcefield for simulating gold surfaces and nanoparticles

We present a ReaxFF reactive forcefield designed to reproduce first-principles density-functional theory (DFT) calculations on gold bulk structures, surfaces, and nanoparticles. We compare the ReaxFF results with those obtained from other atomistic potentials along with results from Perdew-Burke-Ernzerhof–generalized gradient approximation (PBE-GGA) DFT. The new ReaxFF gold force field, which has been trained against various bulk and surface properties calculated by DFT, is subsequently applied to simulated annealing simulations on a range of gold nanoparticles ${\text{Au}}_n$ $\left(n=38,236,1514\right)$.

Figure 1

(Color online) Equations of state for different Au bulk structures calculated by (a) EAM, (b) PBE-GGA, and (c) ReaxFF.

Figure 2

(Color online) Selected Au diffusion pathways on an Au(100) surface. Insets in each figure illustrate the diffusion pathways, where open circles depict vacant sites and filled circles depict adatoms on an Au(100) surface. All diffusion pathways are described in detail in Refs. 49, 60.

Figure 3

(Color online) Comparison between PBE-GGA and ReaxFF calculated total binding energies for molecular gold clusters ${\text{Au}}_n$ $\left(n=2–10\right)$. The models show the most stable structures obtained with DFT.

Figure 4

(Color online) Gold clusters simulated with ReaxFF and their relaxed structures after different temperature annealing procedures.

Figure 5

(Color online) The percent composition of gold atoms with different coordination numbers. The different curves are for the initial bulk-truncated ${\text{Au}}_{1514}$ cluster and after annealing at 1000, 1250, and 1500 K.

Figure 6

(Color online) Illustrations of the ${\text{Au}}_{1514}$ cluster before and after annealing at 1500 K. Atoms are colored according to their coordination numbers. Models on the left show the outer shell of the full nanoparticle, while models on the right show the nanoparticles with cross-sectional cut to show their cores.