More recently, Izadi et al. introduced the optimal point charge family of water models-OPC and OPC3. According to Izadi et al., in liquid water, inter-molecular interactions are heavily influenced by the electrostatic interactions which in turn are governed by the lower-order multipole moments. The higher-order multipole moments are left out. OPC models fit the parameters to reproduce the correct lower-order multipole moments of the water molecule in the condensed phase.