Foce field schemesΒΆ

In molecular simulations, FF parameters are usually derived by some empirical rules, either derived from some experimental observations or quantum mechanical calculations. Different research groups use different rules to obtain these parameters. Collectively, a set of rules that model a class of molecules is called a force field (FF) scheme.

DL_FIELD implements a wide range of FF schemes as shown below:

  • CHARMM - For biomolecules including small drug molecules.
  • AMBER - For biomolecules including small drug molecules..
  • OPLS2005 - For biomolecules, general organic molecules and drug molecules.
  • OPLS-DES - Deep eutectic solvents.
  • OPLS CL&P - Organic cationic and anionic species for ionic liquids.
  • OPLS AA/M - Protein molecules.
  • PCFF - General organic molecules, organic polymers, Si-based structures.
  • CVFF - General organic molecules.
  • TraPPE-EH - Small organic molecules, for phase equilibria simulations.
  • Dreiding - General FF for covalent molecules.
  • Inorgnic - force fields for inorganic materials.
  • CHARMM19 - United atom protein model.
  • G54A7 - united atom Gromos FF.
  • MISC FF - general purpose definable FF.
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FF Scheme Structures

Each FF scheme (XX) consists of the following file components:

  • Structure file (.sf), XX.sf.
  • Parameter file (.par), XX.par.
  • Miscellaneous supporting files for some FF schemes.

These files are located in the lib/ directory and they are all expressed in the same format for all FF schemes.

Some FF schemes are sub-divided for different types or classes of molecules. For instance, CHARMM force fields consist of schemes for amino acids (proteins), nuclei acids (DNA, RNA), carbohydrates and general organic molecules. In DL_FIELD, these sub divisions are considered to be independant FF schemes, although collectively they are compatible to one another.

An FF scheme must always be scpecified in the control file when running DL_FIELD. The program also allows multiple potential scenerios by specifying more than one different FF schemes. For more details, please see Multiple Potential Features.


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Table below lists the available FF schemes with the corresponding scheme labels.

FF schemes Labels Example structures
CHARMM22 for proteins CHARMM22_prot amino acid residues, fitted molecules
CHARMM36 for proteins CHARMM36_prot amino acid residues, fitted molecules
CHARMM36 for nuclei acids CHARMM36_nucl DNA, RNA
CHARMM36 for lipids CHARMM36_lipid lipid molecules
CHARMM36 for carbohydrates CHARMM36_carb sugar molecules
CHARMM36 gneral force field CHARMM36_cgenff organic molecules, biomolecules
Amber including Glycam FF AMBER Amino acids, carbohydrates.
Amber general force field AMBER16_gaff Organic molecules.
OPLS_2005 OPLS2005 General organic molecules.
OPLS AA/M for proteins OPLS_AAM amino acid residues
OPLS CL&P OPLS_CL_P ionic liquids
OPLS for deep eutetic solvents OPLS_DES organic solvent molecules
DREIDING DREIDING General organic molecules
Polymer consistent force field PCFF General molecules, organosilica
Consistent valence force field CVFF General organic molecules
COMPASS COMPASS General organic molecules
Transferable potentials for phase equilibria TRAPPE_EH General organic molecules, small aromatics
Inorganic FF for binary oxides INORGANIC_binary_oxide Mineral oxides, MO2, MO
Inorganic FF for ternary oxides INORGANIC_ternary_oxide Minerals, MXO
Inorganic FF for binary halides INORGANIC_binary_halide MX, X=F, Cl, Br, I
Inorganic FF for glass INORGANIC_glass alumino-silicate, phosphate glass, etc
Inorganic FF for clay INORGANIC_clay Clay minerals, CLAYFF.
Inorganic FF zeolites INORGANIC_zeolite Silicalites, faujasites, etc
Zeolite Hill-Sauer INORGANIC_zeolite_HS silica, aluminasilicic acid, aluminosilicates
CHARMM19 - United atom model CHARMM19 amino acids.
Gromos united atom G54A7 G54A7 Amino acids, lipids.
Non-specific, miscellaneous FF MISC_FF Anything: user define.
Multiple potential multiple Mixed components, bioinorganics.

Example below shows a top portion of an example control file, showing the CHARMM22 protein FF is used.

Control file title. For DL_FIELD 4.10.
1        * Construct DL_POLY output files
0        * Secodary output files (Gromacs, Chemshell or none).
charmm22_prot  * Type of force field require (see list below for choices).
kcal/mol  * Energy unit: kcal/mol, kJ/mol, eV, or K.
normal  * Conversion criteria (strict, normal, loose)
1        * Bond type (0=default, 1=harmonic , 2=Morse)
1        * Angle type (0=default, 1=harmonic, 2=harmonic cos)
...
...

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