INTERFACE MD

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. 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. 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.

A few highlights are: (1) IFF reduces common errors in surface and interfacial energies up to 500% 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 ability of alternative force fields and common DFT. (4) The growing database of surface models covers nanoparticle surface chemistry and the influence of solution pH (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 and for multi-scale simulations, including the QM electronic structure, reactive, and meso-scale simulations, have demonstrated the basic feasibility to model complex problems from individual atoms to the small micrometer scale.

Download latest release (1.5)

View overview presentations

Theory

Usage

Validation

Application

Recent Additions (2017-2018):
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 (xxx.car/xxx.mdf) 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) We are working on a new IFF release that will double the coverage of compounds.

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
2015-05-05
2014-04-15
2013-04-01
2013-01-01
INTERFACE_FF_1_5
INTERFACE_FF_1_3
INTERFACE_FF_1_2
INTERFACE_FF_1_0
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.

interface_concept
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).
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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.
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Please contact hendrik.heinz@colorado.edu for questions and feedback.
Credits to Ratan Mishra, Fateme Emami, Tzu-Jen Lin, Hadi Ramezani-Dakhel.
Recent applications of IFF:
(1) 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.
(2) 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.
(3) 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.
(4) 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.
(5) 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.