  We demonstrate an automatic method of force field development for molecular
simulations. Parameter tuning is taken as an optimization problem in many
dimensions. The parameters are automatically adapted to reproduce known
experimental data such as the density and the heat of vaporization. Our method
is more systematic than guessing parameters and, at the same time saves human
labour in parameterization. It was successfully applied to several molecular
liquids: As a test, force fields for 2-methylpentane, tetrahydrofurane,
cyclohexene and cyclohexane were developed.
