====== OPLS ======
**O**ptimized **P**otentials for **L**iquid **S**imulations

OPLS((Jorgensen WL and Tirado-Rives J, 1988 "The OPLS Force Field for Proteins. Energy Minimizations for Crystals of Cyclic Peptides and Crambin" //J. Am. Chem. Soc.// v.110 pp.1657–1666))
((Jorgensen WL, Maxwell DS and Tirado-Rives J 1996 "Development and Testing of the OPLS All-Atom Force Field on Conformational Energetics and Properties of Organic Liquids" //J. Am. Chem. Soc.// v.118 pp.11225–11236)) 
- a force field with the functional form similar to AMBER.

A distinctive feature of the OPLS parameters is that they were optimized to fit experimental properties of liquids, such as density and heat of vaporization.