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 and in a surface model database. 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 therefore enables access to a plethora of materials interfaces that are yet unknown in experiment and remained inaccessible to molecular simulation previously. A growing database of realistic 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 play a role for quantitative property predictions. The tools enable new directions in the computation-guided discovery of bionanostructures and advanced materials, including QM/MM, reactive, and multi-scale simulation techniques.

   

Download latest release (1.5)

View overview presentation

 
The INTERFACE force field currently includes the PCFF-INTERFACE, CHARMM-INTERFACE, and CVFF-INTERFACE distributions, ready for simulations with Discover, Forcite (Materials Studio), LAMMPS, and NAMD. The package contains parameters and surface models for the following compounds, in addition to the native paramaters for biomolecules, polymers, and solvents in the respective force fields (see Langmuir 2013, 29, 1754):
  • 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 and tobermorite 14 Å.
    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 following versions are available for download (.zip) and the documentation helps 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 transferable to other force fields such as AMBER, OPLS-AA, and Dreiding without modifications. These include fcc metals, apatite, silica, and some cement minerals. Minor adjustments are necessary for other compounds due to scaling of 1,4 nonbond interactions and/or combination rules.

interface_concept
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).
 
Developments in progress include a graphical user interface to construct realistic surface models (composition, facet, protonation state) per mouse-click and to generate automatically 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, organic semiconductors, and other compounds are under way.
hjh
Please contact hendrik.heinz@colorado.edu for feedback and questions.