The MLR potential is based on the classic Morse potential which was first introduced in 1929 by Philip M. Morse. A primitive version of the MLR potential was first introduced in 2006 by Robert J. Le Roy and colleagues for a study on N 2. This primitive form was used on Ca 2, KLi and MgH, before the more modern version was introduced in 2009. A further extension of the MLR potential referred to as the MLR3 potential was introduced in a 2010 study of Cs 2, and this potential has since been used on HF, HCl, HBr and HI.