Ewald summation was developed as a method in theoretical physics, long before the advent of computers. However, the Ewald method has enjoyed widespread use since the 1970s in computer simulations of particle systems, especially those whose particles interact via an inverse square force law such as gravity or electrostatics. Recently, PME has also been used to calculate the r − − 6 part of the Lennard-Jones potential in order to eliminate artifacts due to truncation. Applications include simulations of plasmas, galaxies and molecules.