Skip to main content Module params Copy item path Source UffAtomParams UFF atom type parameters.
Source: Rappé, A. K. et al. “UFF, a full periodic table force field for molecular mechanics
and molecular dynamics simulations.” J. Am. Chem. Soc. 114 (1992): 10024–10035. Table 1. get_uff_angle_force_constant UFF angle bending force constant K_ijk (Rappé eq. 13, simplified).
K_ijk = 332.06 · Z*_i · Z*_k / (r_ij · r_jk · r_ik²)
332.06 ≈ e²Nₐ/(4πε₀) in kcal·Å/e² (Coulomb constant for UFF energy units)
where r_ik² = r_ij² + r_jk² - 2·r_ij·r_jk·cos(θ₀) get_uff_bond_force_constant UFF bond stretching force constant K_ij (Rappé eq. 6).
E_bond = ½ K_ij (r - r₀)² → K_ij = 664.12 · Z*_i · Z*_j / r₀³
664.12 = 2 × 332.06 where 332.06 ≈ e²Nₐ/(4πε₀) in kcal·Å/e² (Coulomb constant) get_uff_bond_length Compute the UFF equilibrium bond length between two atom types. get_uff_params Retrieve UFF parameters by atom type label. get_uff_torsion_params UFF torsion barriers for bond j–k (Rappé Section 3D, eq. 16).
Returns (V_barrier, periodicity_n, cos_phi0).
V_barrier = ½ · √(V_i · V_j) for sp3–sp3 bonds.