Our team develops an all-atom force field, the Interface Force Field (IFF), and a surface model database for the simulation of nanostructures of 1 to 1000 nm size, including minerals, metals, oxides, and (bio)polymers across the periodic table. IFF serves the computation-guided discovery of biomaterials and advanced materials.

We utilize a consistent description of chemical bonding and data-driven validation for compounds across the periodic table that leads to very high accuracy. Parameters and models are understood in-depth for validated compounds and are accompanied by a surface model database to cover critical surface chemistry, such as (hkl) cleavage planes, pH-related surface changes, and common defects for easy customization. The key novelty is the use of one single energy expression for all inorganic and organic compounds across the periodic table, consistent with quantum mechanical principles.

Full understanding and thermodynamic consistency of parameters for the validated model compounds allows property predictions for trillions of yet unknown materials interfaces, e.g., including electrolytes, polymers, and materials combinations. Dependable parameters for the vast space of unexplored compounds (>1060) can also be derived with diminishing effort using our advanced physical interpretation of parameters in combination with automated learning techniques.

Major advances are: (1) IFF covers a lot of previously unparameterized chemical space and reduces common errors up to 500% in surface and interfacial energies in prior models to ~10%, enabling quantitative computations of adsorption, substitution, and assembly. (2) Lattice parameters are up to an order of magnitude more accurate. (3) Chemical accuracy (1 kcal/mol) relative to experiment is often feasible, exceeding the reliability of other force fields and common DFT. (4) The growing database of surface models covers the surface chemistry of nanostructures and the influence of pH values in solution (e.g. silica and apatites), typical cleavage planes, defects and cation exchange capacities (e.g. in clays) that are essential for quantitative property predictions. (5) Extensions for chemical reactions through IFF-R and for multi-scale simulations, including the local QM electronic structure calculations and meso-scale simulations, have demonstrated the feasibility to model complex problems from individual atoms to the micrometer scale.


Download latest release (1.5)

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Recent Additions (2017-2022):
1) Convert input files from Materials Studio format (.car/.mdf) to CHARMM and NAMD format (.pdb/.psf) using the msi2namd tool.
2) Obtain GROMACS format using interfaceff2gro by Andres Vodopivec Kuri (Northeastern U) and interfaceff2gro by Krzysztof Kolman (U Gothenburg). Thank you gyus!
3) Convert Materials Studio format ( to LAMMPS format (xxx.lammps05) using msi2lmp as usual. With pcff_interface the command “% ./msi2lmp.exe xxx -p 2 -c 2 -frc pcff_interface_v1_5.frc -i” with the -i option is recommended to set unnecessary cross-terms to zero (e.g. clays and bonded silicates).
4) A fully developed GUI model builder for calcium-silicate-hydrate phases in cement – the C-S-H Builder. Build a customized initial C-S-H morphology and relax it with the IFF version supplied by energy minimization and MD/annealing before use.
5) Accurate new models for graphitic materials that use virtual pi electrons (graphene, graphite, CNTs, multi-core aromatics, see parameters in the SI).
6) Include covalent metal-thiol interactions by increasing the LJ eps parameter of the S atom in thiols to 1.0 kcal/mol or higher. Easy to implement and yields realistic results (see SI in examples one and two).
7) Accurate new models for MoS2 that exceed the quality prior force fields and DFT.
8) 10 new fcc metals (Ac, Ca (α), Ce (γ), Es (β), Fe (γ), Ir, Rh, Sr (α), Th (α), Yb (β)), including steel alloys with Cr. See complete compilation of bulk and surface models and force field files here.
9) Full set of parameters for calcium sulfates (anhydrite, hemihydrate, gypsum).
10) Full set of parameters for molecular hydrogen, oxygen, and nitrogen, up to two orders of magnitude improved over earlier parameters and compatible with electrolytes, solids, minerals as usual.
11) Polarizable models for gold and Pt (see SI) that additionally capture image charges and responses to electric fields on the fly. Maintain all other advantages of IFF parameters and improve mechanical properties (10-20% agreement with experiments).
12) Concept of IFF-R released to simulate bond breaking reactions (see also separate entry further below).

We encourage you to explore this great resource developed in collaboration with the lab on Wonpil Im, Lehigh University. You can build models, customize models, add biomolecules, and prepare automated input files for simulations with a variety of platforms, including CHARMM, NAMD, LAMMPS, GROMACS, Desmond, and OpenMM in an automated way. We are continuously developing and adding to the functionality of CHARMM-GUI Nanomaterial Modeler. Along with the next steps in development of IFF, a number of new compounds and materials classes will be added.  
14) Parameters for several oxides and hydroxides have been developed and tested, to be released soon. For Al2O3 and NiO, please see our paper in Nano Letters (including the SI with parameters).
15) We continue to work on a new IFF release that will approximately triple the coverage of validated compounds and chemical features compared to version v1.5.

The IFF distribution includes the PCFF-INTERFACE, CHARMM-INTERFACE, and CVFF-INTERFACE force fields, ready for simulations with Discover, Forcite (Materials Studio), LAMMPS, NAMD, and GROMACS, and surface models for the following validated compounds:
  • Clay minerals
    Kaolinite, mica, montmorillonites of different cation density, pyrophyllite. Ready-to-use molecular models of periodic lattices and of cleaved surfaces with equilibrium distributions of cations. The spatial distribution of defect sites agrees with NMR data.
  • Fcc metals
    Ag, Al, Au, Cu, Ni, Pb, Pd, Pt.
    Ready-to-use models of unit cells and rectangular cells of different orientation. The cells facilitate an easy build of {111}, {100}, {110} surfaces and nanostructures such as nanorods and particles.
  • Silica
    Cristobalite, quartz, amorphous silica, as well as all types of silanol and siloxide-terminated surfaces. Includes ready-to-use models of Q2, Q3, Q4, and mixed-chemistry silica surfaces of different degree of ionization in response to specific pH values in solution and silica nanoparticle size. Explanations how to choose models are included.
  • Hydroxyapatite
    Ready-to-use models of the unit cell and all common cleavage planes in response to specific pH values in solution, as well as models of nanocrystallites and sodium hydrogen phosphate/dihydrogen phosphate buffer.
  • Cement minerals (extensive)
    Tricalcium silicate, tricalcium aluminate, ettringite, monosulfate, tobermorite 11 Å, tobermorite 14 Å, C-S-H.
    Ready-to-use models for each mineral, including unit cells, various hydrated phases, and different cleavage planes.
    (CVFF and CHARMM currently support tricalcium silicate and tricalcium aluminate only)
  • Calcium sulfates
    Calcium sulfate (anhydrite), calcium sulfate hemihydrate, and calcium sulfate dihydrate (gypsum).
    Includes models of the unit cells, from which cleavage planes can be easily constructed.
    (currently supported in PCFF only)
  • PEO (poly(ethylene oxide))
    Ready-to-use models of crystalline PEO and a PEO example chain (MW ~2000 g/mol) in water, which can be customized for chains and copolymers of different length can be constructed.
    (currently supported in PCFF only)

The parameters can be combined with existing parameters for biomolecules, polymers, and solvents in the respective parent force fields (CHARMM, PCFF, CVFF). IFF uses default combination rules for atoms in different compounds, needs no additional assumptions about interfacial interactions, and no extra fit parameters (see Langmuir 2013, 29, 1754). Below are the current and all prior versions for download (.zip). Every release includes ready-to-use files with full documentation – it takes only minutes to run first simulations with Materials Studio (Discover/Forcite), LAMMPS, or NAMD:

Date File for Download Comments
latest release 1.5
2012-08-01 to 2010-03-01 CHARMM_METAL same as CHARMM-INTERFACE with metals only
2013-01-01 to 2008-03-01 FF_LS_METAL Parameters and models for clay minerals and fcc metals embedded in PCFF and CVFF
2010-07-01 to 2008-03-01 FF_PHYLLOSILICATES Parameters and models for clay minerals embedded in PCFF and CVFF

Parameters for several compounds can also be embedded without modifications in other force fields such as AMBER, OPLS-AA, and Dreiding: fcc metals, apatite, calcium sulfates, and some cement minerals. For the other compounds, minor adjustments are necessary due to force field-specific scaling of nonbond interactions between 1,4  bonded atoms and/or combination rules.

The Interface force field is compatible with many biomolecular and materials-oriented force fields as it uses a common polynomial energy expression (and offers a choice for either 12-6 or 9-6 Lennard-Jones potentials).
IFF has also been applied to simulate chemical reactions since 2008 by specifying changes in conformation and in bond connectivity, and for accurate rate predictions in catalysis. Routine inclusion of bond breaking and formation is also feasible by replacing harmonic bond potentials with Morse potentials. Developments in-progress include a graphical user interface to construct realistic surface models (composition, facet, protonation state) and to automate the generation of simulation input for all major molecular dynamics programs (programs not yet mentioned above). IFF extensions to further 2D materials (chalcogenides, graphitic structures), bcc/hcp metals, alloys, oxides, and organic semiconductors are in progress.
IFF-R: Simulate Bond Breaking and Stress-Strain Curves Up to Failure
Recent extensions of IFF to IFF-R allow the simulation of bond breaking in molecules and nanostructures, useful to compute the stress-train curves of bulk and hybrid materials up to failure. The concept is the replacement of the harmonic bond stretch potentials by Morse potentials for “breakable” bonds. It is possible to use a clean replacement without adjustment of other parameters.
An easy implementation is available in LAMMPS (using the IFF-PCFF version and a few edits). Step-by-step examples for failure of a CNT and polymer matrix are given in the tutorial below, including  a brief ppt tutorial, input files, test results, and IFF-R Morse bond parameters:



A publication with full documentation is in progress.

Please contact for questions and feedback. Credits to Ratan Mishra, Fateme Emami, Tzu-Jen Lin, Hadi Ramezani-Dakhel, Chandrani Pramanik, Krishan Kanhaiya, Shiyi Wang, Tariq Jamil, Juan Liu, Jordan Winetrout, and all in-kind contributors and users.

Recent applications of IFF:

(1) Kanhaiya, K.; Heinz, H., Adsorption and Diffusion of Oxygen on Pure and Partially Oxidized Metal Surfaces in Ultrahigh Resolution. Nano Lett. 2022, 22, 5392-5400.
(2) Hoff, S. E.; Di Silvio, D.; Ziolo, R. F.; Moya, S. E.; Heinz, H., Patterning of Self-Assembled Monolayers of Amphiphilic Multisegment Ligands on Nanoparticles and Design Parameters for Protein Interactions. ACS Nano 2022, 16, 8766-8783.
(3) Akkineni, S.; Zhu, C.; Chen, J.; Song, M.; Hoff Samuel, E.; Bonde, J.; Tao, J.; Heinz, H.; Habelitz, S.; De Yoreo James, J., Amyloid-like Amelogenin Nanoribbons Template Mineralization via a Low-energy Interface of Ion Binding Sites. Proc. Natl. Acad. Sci. U. S. A. 2022, 119, e2106965119.
(4) Wang, S.; Zhu, E.; Huang, Y.; Heinz, H., Correlation of Oxygen Adsorption on Platinum-Electrolyte Interfaces with the Activity in the Oxygen Reduction Reaction. Sci. Adv. 2021, 7, eabb1435.
(5) Odegard, G. M.; Patil, S. U.; Deshpande, P. P.; Kanhaiya, K.; Winetrout, J. J.; Heinz, H.; Shah, S. P.; Maiaru, M., Molecular Dynamics Modeling of Epoxy Resins Using the Reactive Interface Force Field. Macromolecules 2021, 10.1021/acs.macromol.1c01813 (online).
(6) Jamil, T.; Javadi, A.; Heinz, H., Mechanism of Molecular Interaction of Acrylate-Polyethylene Glycol Acrylate Copolymers with Calcium Silicate Hydrate Surfaces. Green Chem. 2020, 22, 1577-1593.
(7) Mark, L. O.; Zhu, C.; Medlin, J. W.; Heinz, H., Understanding the Surface Reactivity of Ligand-Protected Metal Nanoparticles for Biomass Upgrading. ACS Catal. 2020, 10, 5462-5474.
(8) Zhou, J.; Yang, Y.; Yang, Y.; Kim, D. S.; Yuan, A.; Tian, X.; Ophus, C.; Sun, F.; Schmid, A. K.; Nathanson, M.; Heinz, H.; An, Q.; Zeng, H.; Ercius, P.; Miao, J., Observing Crystal Nucleation in Four Dimensions Using Atomic Electron Tomography. Nature 2019, 570 (7762), 500-503.
(9) Chen, J.; Zhu, E.; Liu, J.; Zhang, S.; Lin, Z.; Duan, X.; Heinz, H.; Huang, Y.; Yoreo, J. J. D., Building Two-Dimensional Materials One Row at a Time: Avoiding the Nucleation Barrier. Science 2018, 362, 1135-1139.
(10) Nathanson, M.; Kanhaiya, K.; Pryor, A.; Miao, J.; Heinz, H., Atomic-Scale Structure and Stress Release Mechanism in Core–Shell Nanoparticles. Acs Nano 2018, 12, 12296-12304.
(11) Zhu, E.; Wang, S.; Yan, X.; Sobani, M.; Ruan, L.; Wang, C.; Liu, Y.; Duan, X.; Heinz, H.; Huang, Y., Long-Range Hierarchical Nanocrystal Assembly Driven by Molecular Structural Transformation. J. Am. Chem. Soc. 2018, DOI: 10.1021/jacs.8b08023.
(12) Pramanik, C.; Gissinger, J. R.; Kumar, S.; Heinz, H., Carbon Nanotube Dispersion in Solvents and Polymer Solutions: Mechanisms, Assembly, and Preferences. Acs Nano 2017, 11, 12805-12816.
(13) Mishra, R. K.; Mohamed, A. K.; Geissbühler, D.; Manzano, H.; Jamil, T.; Shahsavari, R.; Kalinichev, A. G.; Galmarini, S.; Tao, L.; Heinz, H.; Pellenq, R.; Van Duin, A. C.; Parker, S. C.; Flatt, R. J.; Bowen, P., CEMFF: A Force Field Database for Cementitious Materials Including Validations, Applications and Opportunities. Cem. Concr. Res. 2017, 102, 68-89.