VALBOND

In molecular mechanics, VALBOND is a method for computing the angle bending energy that is based on valence bond theory.[1] It is based on orbital strength functions, which are maximized when the hybrid orbitals on the atom are orthogonal[broken anchor]. The hybridization of the bonding orbitals are obtained from empirical formulas based on Bent's rule, which relates the preference towards p character with electronegativity.

The VALBOND functions are suitable for describing the energy of bond angle distortion not only around the equilibrium angles, but also at very large distortions. This represents an advantage over the simpler harmonic oscillator approximation used by many force fields, and allows the VALBOND method to handle hypervalent molecules[2] and transition metal complexes.[3][4] The VALBOND energy term has been combined with force fields such as CHARMM[5] and UFF to provide a complete functional form that includes also bond stretching, torsions, and non-bonded interactions.

  1. ^ Root, D. M.; Landis, C. R.; Cleveland, T. Valence Bond Concepts Applied to the Molecular Mechanics Description of Molecular Shapes. 1. Application to Nonhypervalent Molecules of the P-Block. J. Am. Chem. Soc. 1993, 115, 4201-4209.
  2. ^ Cleveland, T.; Landis, C. R. Valence Bond Concepts Applied to the Molecular Mechanics Description of Molecular Shapes. 2. Application to Hypervalent Molecules of the P-Block. J. Am. Chem. Soc. 1996, 118, 6020-6030. doi:10.1021/ja9506521
  3. ^ Landis, C. R.; Cleveland, T.; Firman; T. K. Valence Bond Concepts Applied to the Molecular Mechanics Description of Molecular Shapes. 3. Application to Transition Metal Alkyls and Hydrides. J. Am. Chem. Soc. 1998, 120, 2641-2649. doi:10.1021/ja9734859
  4. ^ Firman; T. K.; Landis, C. R. Valence Bond Concepts Applied to the Molecular Mechanics Description of Molecular Shapes. 4. Transition Metals with π-Bonds. J. Am. Chem. Soc. 2001, 123, 11728-11742. doi:10.1021/ja002586v
  5. ^ Cite error: The named reference :0 was invoked but never defined (see the help page).