Coarse-grained (CG) models are commonly used to access large system sizes and the long timescales required to observe interesting phenomena. While many methods and procedures exist for deriving CG force fields, the iterative Boltzmann inversion (IBI) method[1] has become a popular choice due to its straightforward nature and general applicability. However, the IBI method, like most approaches for deriving CG force fields, tends to generate force fields that demonstrate strong statepoint dependence. To overcome this limitation, we have developed a multistate extension to the iterative Boltzmann inversion CG potential derivation algorithm, termed multistate iterative Boltzmann inversion (MS IBI).[2] In MS IBI, a CG potential is iteratively updated to match target radial distribution functions across a range of thermodynamic and physical states, adding constraints to the force field optimization process. As such, the final potential demonstrates an increased level of transferability between states. The efficacy and advantages of using MS IBI to derive generally applicable CG force fields is further demonstrated in this work through two case studies. First, MS IBI is used to rederive the k-means CG water model[3] using both bulk and interfacial states, improving the quality of the forcefield.[4] Second, CG force fields for lipid systems of a ceramide sphingolipid and free fatty acid are derived and combined with surface wetting simulations.[5] The latter ensures hydrophobicity is accurately captured such that the contact angle of a water droplet on each surface matches detailed atomistic simulations, overall creating CG force fields that show close agreement atomistic and experimental results.
References
[1] 1. Reith, D., Putz, M. & Müller-Plathe, F. Deriving Effective Mesoscale Potentials from Atomistic Simulations. J. Comput. Chem. 24, 1624â??1636 (2003).
[2] Moore, T. C., Iacovella, C. R. & McCabe, C. Derivation of coarse-grained potentials via multistate iterative Boltzmann inversion. J. Chem. Phys. 140, (2014).
[3] Hadley, K. R. & McCabe, C. On the investigation of coarse-grained models for water: balancing computational efficiency and the retention of structural properties. J. Phys. Chem. B 114, 4590â??9 (2010).
[4] Moore, T. C., Iacovella, C. R. & McCabe, C. Development of a coarse-grained water forcefield via multistate iterative Boltzmann inversion. Mol. Mod. and Sim.: Applications and Perspectives, in press (2016). arXiv:1509.07887
[5] Moore, T. C., Iacovella, C. R., Hartkamp, R. & McCabe, C. A Coarse-grained Model of Stratum Corneum Lipids: Free Fatty Acids And Ceramide NS. Submitted.
