[gmx-users] Why the individual interaction potentials are additive?

[ibrahim khalil]

Dear GROMACS users,

I had a somewhat of a basic (or elementary) question.

While doing MD simulations, we use interaction potentials that consist of
bonded and nonbonded potential terms- then again the bonded term consists
of some other potential terms such as bond, angle, dihedral etc.

My question is-*Why the terms are additive?*

Inside this book of R. LeSar, Introduction to Computational Materials
Science, 2013, I found- the potential energy of a system can be expanded as
a series of terms involving pair, triplets and quadriples of atoms etc. and
we ignore the rest of the higher interaction terms.

-which might explain the bonded interactions being additve.

But why the nonbonded interactions are additive to the bonded ones?