A pair potential specifies an interaction energy for each pair of particles, with total energy given by the sum over distinct pairs. For a radial difference-only potential
in 
, the energy is
 |
Stability means that 
for some constant 
,
for every finite particle configuration. This linear lower bound prevents the energy per particle from diverging
to minus infinity as particles accumulate. An integrable tail satisfies 
for some 
.
