Determining force field parameters using a physically based equation of state.

摘要: Force field parameters used in classical molecular simulations can be estimated from quantum mechanical calculations or spectroscopic measurements. This especially applies to bonded interactions such as bond-stretching, bond-bending, and torsional interactions. However, it is difficult computational expensive obtain accurate describing the nonbonded van der Waals mechanics. In many studies, these are adjusted reproduce experimental data, vapor-liquid equilibria (VLE) data. Adjusting force VLE data currently a cumbersome computationally task. The reason that result of calculation depends on all atom types system, therefore requiring time-consuming iterations. this work, we use an analytical equation state, perturbed chain statistical associating fluid theory (PC-SAFT), predict results for VLE. PC-SAFT state approximate objective function f(p) array p. here example defined deviations vapor pressure, enthalpy vaporization liquid density with respect optimized using which orders magnitude quicker calculate than simulation. solution excellent approximation real function, so resulting method requires only very few simulation runs converge. illustrated by optimizing transferable Lennard-Jones n-alkane series. Optimizing four p = (e(CH(2))(CH(2)), e(CH(3))(CH(3)), σ(CH(2))(CH(2)), σ(CH(3))(CH(3))) agreement coexisting densities, pressure caloric properties within 2 -3 runs.