Hard dumbbells,
hard spherocylinders, etc. 
if overlap otherwise

First approximation to rigid molecules

Interaction site models, rigid 
sum of isotropic pair energies
,
where several
interaction sites and are in fixed positions on molecules
and , respectively

Rigid molecules

Interaction site models with nonrigid bonds 
sum of isotropic pair energies, both intra and intermolecular

Nonrigid molecules

Kramerstype 
sum of isotropic pair energies, exclusively between sites on different
molecules; certain intramolecular distances (bonds) and/or angles
are fixed

Flexible molecules, from ethane to biopolymers

Stockmayer 
LennardJones + point dipoles

First approximation to small polar molecules 
Anisotropic Kihara 
where is the shortest distance between two linear rods

Rigid linear molecules
with distributed
LennardJones interaction 
GayBerne 
where and depend on
and certain substancespecific
shape parameters

Liquid crystal molecules of ellipsoidal shape, with
smoothly distributed LennardJones sites
