Skip to toolbar

Integral Equation Coarse-Graining Method

The Integral Equation Coarse-Graining (IECG) software is based on the IECG theoretical approach to coarse-grain polymer liquids.[1] In the IECG model a polymer chain is represented as a collection of soft beads, or particles, each including a chain fragment of thirty monomers or higher. In its most efficient description, each polymer chain is described as one soft sphere, interacting through the IECG potential.

The IECG reduced representation ensures a considerable computational speed up in Molecular Dynamics or Monte Carlo simulations of polymer liquids (for example, up to eight orders of magnitude for a liquid of polymers with degree of polymerization N=300 at 503 K with a monomer density of 0.03296 Å).[2]

Because IECG reproduces with accuracy the equation of state (the pressure) of an atomistic simulation, the IECG software ensures consistency in all the thermodynamic properties that can be calculated from the pressure, such as the excess free energy (by thermodynamic integration of the pressure).[3] IECG also reproduces with accuracy the structure of the liquid, as represented by pair distribution functions. However, because degrees of freedom are eliminated during coarse-graining, the IECG method does not ensure consistency in the entropy and the internal energy with the atomistic system.  Those properties need to be corrected to reproduce the atomistic values (please stay tuned, as entropy and internal energy upgrade codes will be made available in the future).[4]

The IECG potential has been solved analytically, which ensures the transferability of the model.[5],[6]  Tests of IECG have shown its accuracy in predicting pair distribution functions and pressure, in agreement with atomistic simulations of polyethylene (PE) in different thermodynamic conditions. The dynamics, properly rescaled, reproduces the dynamics of the atomistic simulation.[7],[8]

The IECG software on this site allows you to calculate the effective IECG potential for a liquid of polymer chains in your selected representation.

The IECG software has been developed by contributing researchers  at the University of Oregon for your internal, non-profit research use. The university and the developers are delighted to make this available under the conditions described in the IECG Software Academic Commons License Agreement.

Please review the full licensing agreement prior to downloading the software. 

[1] Guenza, M. G, Dinpajooh, M., McCarty, J., Lyubimov, I. Y. (2018). Accuracy, Transferability, and Efficiency of Coarse-Grained Models of Molecular Liquids. The Journal of Physical Chemistry, B, 122(45), 10257-10278  DOI: 10.1021/acs.jpcb.8b06687.

[2] Dinpajooh, M., Guenza, M. G. (2018). Coarse-graining simulation approaches for polymer melts: the effect of potential range on computational efficiency. Soft Matter, 14, 7126-7144 .

[3] Dinpajooh, M. & Guenza, M. G. (May 2017). Thermodynamic Consistency in the Structure-Based Integral Equation Coarse-Grained Method. Polymer, 117: 282–286,

[4] McCarty, J., Clark, A. J., Copperman, J., Guenza, M. G. (2014). An Analytical Coarse-Graining Method which Preserves the Free Energy, Structural Correlations, and Thermodynamic State of Polymer Melts from the Atomistic to the Mesoscale.  J. Chem. Phys, 140, 204913.

[5] Clark, A. J., Mccarty, J., Lyubimov, I. Y., Guenza, M. G. (2012). Thermodynamic Consistency in Variable-Level Coarse Graining of Polymeric Liquids. Phys. Rev. Lett., 109, 168301.

[6] Clark, A. J., McCarty, J., Guenza, M. G. (2013). Effective Potentials for Representing Polymers in Melts as Chains of Interacting Soft Particles.  J. Chem. Phys., 139, 124906.

[7] Lyubimov, I. Y. & Guenza, M. G. (September 2011). First-Principle Approach to Rescale the Dynamics of Simulated Coarse-Grained Macromolecular Liquids. Physical Review, E 84, no. 3: 031801-19,

[8] Lyubimov, I. Y. & Guenza, M. G. (March 2013,). Theoretical Reconstruction of Realistic Dynamics of Highly Coarse-Grained Cis -1,4-Polybutadiene Melts. The Journal of Chemical Physics 138, no. 12: 12A546-13,