Lennard-Jones fluid
# Lennard-Jones fluid

A Lennard-Jones fluid is a computational model widely used in computational chemistry to study intermolecular interactions. It is named after John Lennard-Jones, who introduced the Lennard-Jones potential, also known as the LJ potential or 12-6 potential, that describes the interactions between particles in the fluid. The LJ potential captures the essential features of electronically neutral atoms or molecules, including repulsive and attractive van der Waals interactions.

The LJ potential is given by the equation:

$V_{\text{LJ}}(r)=4\varepsilon \left[\left({\frac {\sigma }{r}}\right)^{12}-\left({\frac {\sigma }{r}}\right)^{6}\right]$

Here, V represents the distance between two interacting particles, ε is the depth of the potential well (dispersion energy), and σ is the distance at which the potential energy is zero (size of the particle). The LJ potential exhibits a repulsive force at very close distances, an attractive force at moderate distances, and no interaction at infinite distance.

Molecular dynamics simulations have been used to study the Lennard-Jones fluid under various state conditions. These simulations provide information about the pressure and configurational energy of the fluid at different densities and temperatures.

A comprehensive equation of state for the Lennard-Jones fluid has been derived by combining simulation results with values calculated from the virial series and second virial coefficients. This equation of state, known as the modified Benedict–Webb–Rubin equation, incorporates 33 constants and accurately describes the behavior of the Lennard-Jones fluid over a wide range of temperatures and densities.

Additionally, two- and three-body integrals (J, K, and L) that occur in perturbation theory for molecular fluids have been calculated for the Lennard-Jones fluid under various state conditions.

