Non-bonded interactionsΒΆ

The inter-molecular or nonbonded interactions consist of energy components interact between pairs of atoms and depend only on the interatomic distances.

../../_images/Orange_bar2.png

Nonbonded interactions consist of several energy components as follows:

  • Electrostatic (Coulombic) interactions. This arises due to charges on atoms and they are considered long-range in nature.
  • Dispersive (van der Waals) interactions. Such interactions are due to electron cloud fluctuations, forming instanteneous dipoles. They can be found even in inert gas systems and neutral atoms.
  • Urey-Bradley (UB) 1-3 atom pair interactions - This is specific to CHARMM FF schemes. They correlate with the angle interactions. Diagram below shows the UB interactions for the benzene molecule.
  • Others. This includes dipole-dipole interactions such as the hydrogen bonds, charge-dipole interactions, etc. However, most FF schemes do not explicitly include such interactions as they are implicitly included in the above mentioned interactions.
Urey-Bradley interactions

Note

For covalent molecules nonbonded interactions do not apply to 1-2 and 1-3 bonded atoms, except the UB interactions. For the 1-4 atoms, a constant scaling factor is usually applied, depending on the FF schemes.

^ GO TO TOP ^