INTERFACE MD

The Heinz team develops all-atom force fields to simulate nanostructures of 1 to 100 nm size in high accuracy, including minerals, metals, and oxides. The parameters and models for validated compounds are summarized in the INTERFACE force field (IFF) and accompanied by a surface model database to support relevant surface chemistry (cleavage planes, pH, common defects). The force field integrates previously incompatible energy expressions for materials oriented simulations and for biomolecular simulations into one thermodynamically consistent platform for the simulation of complex interfaces and compounds across the periodic table.

The INTERFACE platform supports the computation-guided discovery of biomaterials and advanced materials. It does so by enabling access to trillions of materials interfaces yet unknown in experiment and inaccessible by prior molecular simulation. Errors in interfacial energies and derivatives are reduced from up to 500% previously to <10%, and lattice parameters about an order of magnitude more accurate. IFF reaches chemical accuracy (1 kcal/mol) relative to experiment in many cases, clearly exceeding the accuracy of other force fields and often that of DFT. The growing database of surface models covers nanoparticle surface chemistry and a range of pH values (e.g. silica and apatites), typical cleavage planes, as well as defects and cation exchange capacities (e.g. in clays) that are essential for quantitative property predictions. IFF can be coupled with QM/MM, reactive, and multi-scale simulation techniques.

Download latest release (1.5)

View overview presentations

Theory

Usage

Validation

Application

Recent Additions (2017-2018):
1) For the efficient conversion of input files in Materials Studio format (.car/.mdf) to CHARMM and NAMD format (.pdb/.psf), please use our new msi2namd tool.
2) For conversion to GROMACS format, a new interfaceff2gro tool is available, written by Krzysztof Kolman (U Gothenburg).
3) For the conversion from Materials Studio format (xxx.car/xxx.mdf) to LAMMPS format (xxx.lammps05) with pcff_interface, consider using the command “% ./msi2lmp.exe xxx -p 2 -c 2 -frc pcff_interface_v1_5.frc -i” with the -i option to set unnecessary cross-terms to zero (e.g. in clays and bonded silicates).
4) A new model builder for calcium-silicate-hydrate phases in cement, the C-S-H Builder, is available. You can install this fully developed GUI to build a customized initial C-S-H morphology and relax it with the IFF version supplied in the same folder by energy minimization and MD/annealing before use.
5) Accurate models for graphitic materials that include virtual pi electrons (graphene, graphite, CNTs, multi-core aromatics) are available. Please download from the Supporting Information.
6) Covalent-like metal-thiol interactions can in good approximation be described by increasing the LJ eps parameter of the S atom to 1.0 kcal/mol or higher. This method is easy to implement and yields realistic results (see SI in published examples one and two)
7) A new IFF release is expected soon – we expect to double the coverage of compounds and maintain full compatibility with the current release (1.5).

The INTERFACE force field includes the PCFF-INTERFACE, CHARMM-INTERFACE, and CVFF-INTERFACE distributions, ready for simulations with Discover, Forcite (Materials Studio), LAMMPS, and NAMD. We include parameters and surface models for the following compounds:
  • Clay minerals
    Kaolinite, mica, montmorillonites of different cation density, pyrophyllite. Includes 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.
    Includes 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
    Models of cristobalite and quartz 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 that represent specific pH values and silica nanoparticle sizes. Explanations how to choose models are included.
  • Hydroxyapatite
    Ready-to-use models of the unit cell and all common cleavage planes for specific pH values, 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.
    Includes 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))
    Includes ready-to-use models of crystalline PEO and an example chain (MW ~2000 g/mol) in water, from which models of 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 force fields. Default combination rules are applied and no additional assumptions about interfacial interactions and no extra fit parameters are necessary (see Langmuir 2013, 29, 1754). The following versions are available for download (.zip), which include full documentation for an easy start:

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

Several parameters are also transferable to other force fields such as AMBER, OPLS-AA, and Dreiding without modifications. These include fcc metals, apatite, calcium sulfates, and some cement minerals. For other compounds, minor adjustments are necessary due to scaling of 1,4 nonbond interactions between bonded atoms and/or combination rules.

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Figure 1. The INTERFACE force field is compatible with common biomolecular and materials-oriented force fields as it uses a common polynomial energy expression (both 12-6 and 9-6 Lennard-Jones parameters).
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IFF has also been applied to simulate chemical reactions since 2008 by specifying changes in conformation and in bond connectivity using input parameters from experiment and quantum mechanics, and for accurate rate predictions in catalysis.  We are working on the routine inclusion of bond breaking and formation since the feasible accuracy is one order of magnitude higher than with other methods. Further developments in progress include a graphical user interface to construct realistic surface models (composition, facet, protonation state) per mouse-click and to automatically generate simulation input for inorganic-(bio)organic systems that is compatible with major molecular dynamics programs (LAMMPS, GROMACS, NAMD, others). Extensions of the force field and surface models for graphitic structures, bcc/hcp metals, alloys, further oxides, and organic semiconductorsother compounds 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.