Fig. 1. Schematic of atomic configurations in energy terms: (a) 1-body, (b) 2-body, (c) 3-body, (d) 4-body, (e) hydrogen–bonding and (f) noncovalent interactions, respectively. A gray sphere represents the position of the primary atom in each energy term. Open bars represent covalent bonds, while dotted lines are noncovalent bonds.

Fig. 2. (A) Schematic of the spatial decomposition consists of sub-domains Ω₀–Ω₃. On the sub-domain Ω₀ atom information from neighbor domains (Ω₁, Ω₂ and Ω₃ are stored in the buffer layer with the thickness L_b shown as shaded area surrounding Ω₀. The primary atoms in each cluster (gray spheres) must be in Ω₀, while other atoms (white spheres) may be copied from neighbor domains. (B) An example of 4-body atom configuration on a domain boundary. The explicit atoms are shown with solid-line spheres and bonds (i,j,k, and l), and so are implicit atoms with dotted-line spheres and bonds (m₁–m₅). Here jth atom is the primary of the cluster. In this example, the deepest level from the primary atom is l_max=3.

Fig. 3. Isogranular parallel efficiency of the parallel ReaxFF algorithm as a function of the number of processors on (A) IBM Blue Gene/L with the number of atoms per processor N/P=10,752, (B) SGI Altix 3000 with N/P=36,288, and (C) AMD dual-core Opteron cluster with N/P=107,520.

Fig. 4. Execution time of the parallel ReaxFF program as a function of the number of atoms on 131,072-processor IBM Blue Gene/L, 1920-processor SGI Altix 3000, and 2048-core AMD Opteron.

Bond-order calculation algorithm

Classification of interaction functions

Force calculation arising from the derivative of BO_ij

Force-calculation arising from the derivative of Δ_i

1-body force calculation

2-body force calculation

3-body force calculation

4-body force calculation

Hydrogen–bonding force calculation

Noncovalent force calculation

Electronegativity-equalization computation

Multiple time-step algorithm

The parameters in the bond-order functions

The parameters in the 1-body energy

The parameters in the E_bond

The parameters in the 3-body energy

The parameters in the 4-body energy

The parameters in the hydrogen–bonding energy

The parameters in the noncovalent energy