Computational cost is also kept to a minimum in standard transferable FFs by assigning the L-J parameters from a library of pre-fit parameters. This has become standard practice across transferable FFs, with OPLS3 containing 124 different atom types so far, and many general FFs borrowing terms from their biological counterparts. The L-J potential parameters are often tuned to accurately recreate experimental liquid properties. While this technique works very well for atoms covered in the original parameterization, more atom types often have to be introduced to account for new chemical environments. During the optimization of the GAMMP/GAFF-LJ* parameters, for example, it was found that for a test set of 430 compounds the 41 standard atom types of GAFF were restricting the maximum achievable accuracy of the FF. The performance was then substantially increased with the addition of 11 new atom types, reducing the average unsigned relative error in the heat of vaporization from 17.9% to 5.9%. Clearly increasing the number of atom types will help increase the overall accuracy of a FF as new exceptions to current atom types arise. Logically this implies that system-specific FF parameters have the potential to lead to an overall more accurate FF.