Table 1. Force Field Parameters for the Metal Dummy Models Presented in This Work.
| Bonded Parameters | |||||
|---|---|---|---|---|---|
|
b0 (Å) |
|||||
| bond typea | Kb (kcal mol–1 Å–2) | MG | AL | FE | CR |
| M-Di | 800.0 | 0.90 | 1.10 | 1.10 | 1.10 |
| angle typeb | Kθ (kcal mol–1 rad–2) | θ (degrees) | |||
|---|---|---|---|---|---|
| Di-M-Di | 125.0 | 180.0 | |||
| Di-M-Dj | 125.0 | 90.0 | |||
| Nonbonded Parameters | |||||
|---|---|---|---|---|---|
| atom typec | mass | charge | Rmin/2 (Å) | ε (kcal mol–1) | C4 (kcal mol–1 Å–4) |
| MG (minC4) | 6.305 | –1.0 | 0.579 | 118.3569 | 1.0 |
| MG (midC4) | 6.305 | –1.0 | 0.706 | 26.8375 | 67.0 |
| MG (maxC4) | 6.305 | –1.0 | 1.045 | 0.9768 | 149.0 |
| AL | 8.982 | –1.2 | 0.725 | 12.4578 | 214.0 |
| FE | 37.845 | –1.2 | 0.796 | 32.4579 | 324.0 |
| CR | 33.996 | –1.2 | 0.670 | 57.3268 | 180.0 |
| D (Mg2+) | 3.00 | 0.5 | 0 | 0 | 0 |
| D (Al3+) | 3.00 | 0.7 | 0 | 0 | 0 |
| D (Fe3+) | 3.00 | 0.7 | 0 | 0 | 0 |
| D (Cr3+) | 3.00 | 0.7 | 0 | 0 | 0 |
a
Ub = Kb(b – b0)2, where Kb is the force constant and b0 is the equilibrium bond length.
b
Uθ = Kθ(θ – θ0)2, where Kθ is the force constant and θ0 is the equilibrium angle. M and D denote the central metal ion and the dummy atom, respectively. The subscripts i and j on the dummy atoms distinguish between dummy atoms that are collinear or perpendicular to each other.
c
MG, AL, FE, and CR denote the central Mg2+, Al3+, Fe3+, Cr3+ ions, respectively. The three different Mg2+ models, minC4, midC4, and maxC4, mainly differ in the magnitude of the C4 term, with min, mid, and max denoting the relevant magnitude of the C4 terms (Rmin and ε were then adjusted accordingly to the C4 term used).