# Buckingham potential

The Buckingham potential is given by [1]

$\Phi _{{12}}(r)=A\exp \left(-Br\right)-{\frac {C}{r^{6}}}$

where $\Phi _{{12}}(r)$ is the intermolecular pair potential, $r:=|{\mathbf {r}}_{1}-{\mathbf {r}}_{2}|$, and $A$, $B$ and $C$ are constants.

The Buckingham potential describes the exchange repulsion, which originates from the Pauli exclusion principle, by a more realistic exponential function of distance, in contrast to the inverse twelfth power used by the Lennard-Jones potential. However, since the Buckingham potential remains finite even at very small distances, it runs the risk of an un-physical "Buckingham catastrophe" at short range when used in simulations of charged systems. This occurs when the electrostatic attraction artificially overcomes the repulsive barrier. The Lennard-Jones potential is also about 4 times quicker to compute [2] and so is more frequently used in computer simulations.