Force Fields

There may be a delay from the time a potential is reported in our papers to the release of the simulation files on this page. It is our pleasure to share every model published. If there is a model you would like, but not listed on this page. Please send me an email (see email address at the bottom of the page).

Water force fields developed with Adaptive Force Matching (AFM)

(To open these files, please run tar -xvzf filename.tgz)

BLYPSP_4F.

This model was created by fitting coupled cluster quality forces for liquid water from 0 ºC to 40 ºC.
This model is recommended for all liquid phase simulations.
These files can be used without modification with Gromacs 4.5, 4.6 and 5.x.
If you have gromacs 4.6.x installed, you can simulate the model system provided by exectuting:

grompp_d -n index.ndx -p BLYPSP-4F.top
mdrun_d -nt 6 -table BLYPSP-4F -tableb BLYPSP-4F

When using this model, please cite: “Approaching Post-Hartree-Fock Quality Potential Energy Surfaces with Simple Pair-wise Expressions: Parameterizing Point-Charge Based Force Fields for Liquid Water Using the Adaptive Force Matching Method” Feng Wang, Omololu Akin-ojo, Eric Pinnick, Yang, Song, Molecular Simulation, 37, 591 (2011)

rWAIL. flexible version.
rWAIL EG273 variant. rigid version optimized for lower temperatures <= 273 K.
rWAIL EG298 variant. rigid version optimized for ambient or higher temperatures => 298 K.

This model is the improved 2024 model for simulation of ice or ice-water equilbrium and study supercooled water.

When using this model, please cite: “Water Potential from Adaptive Force Matching for Ice and Liquid with Revised Dispersion Predicts Supercooled Liquid Anomalies in Good Agreement with Two Independent Experimental Fits ”, Raymond Weldon, and Feng Wang, J. Phys. Chem. B., 128, 3398 (2024)

WAIL.

This model was designed for simulation of ice or ice-water equilbrium. The rWAIL model above is the prefered model.
For simulation of pure water, please use the BLYPSP-4F model above.

When using this model, please cite: “Predicting the melting temperature of ice-Ih with only electronic structure information as input ”, Eric Pinnick, Shyam Erramilli, and Feng Wang, J. Chem. Phys., 137, 014501 (2012)

B3LYPD_4F

This is another model designed for simulation of liquid water. The model was created by fitting forces calculated with B3LYP with an SAPT based dispersion correction.
For all practial purpose, the BLYPSP-4F model is better.

If you do decide to use this model, please cite: “The Quest for the Best Non-polarizable Force Field for Water from the Adaptive Force Matching Method” Omololu Akin-ojo, and Feng Wang, J. Comput. Chem., 32, 453, (2011)

Effective Centroid Potential for H₂O or D₂O.

This models capture centain nuclear quantum effects for H₂O and D₂O.

If you use these of models, please cite: “The strengths and limitations of effective centroid force models for calculating properties of liquid water", Ying Yuan, Jicun Li, Xin-Zheng Li, Feng Wang*, J. Chem. Phys., 148, 184102, (2018)”

Ion Water Potentials developed by fitting MP2 forces using AFM.

MP2_766.

This file contains all the models for alkaline ions (Li⁺, Na⁺, K⁺, Rb⁺, and Cs⁺) and the halide ions (F^-, Cl^-, Br^-, I^-). The effecitve ionic charges are constrained to 0.766e in these models. Cross terms between cations and anions are also provided.

Sample files for simulation of NaCl, KBr, and CsI are provided.

These files can be used with Gromacs version 4.5, 4.6 and 5.x.
With gromacs 4.6.x, you should be able simulation the examples by executing (bash)

export GMXLIB=/home/fengwang/razor/models/IonAFM/IonAFM_766/GMXLIB
grompp -n index.ndx
mdrun -nt 6 -table Ion.SAPT-MS.766 -tableb Ion.SAPT-MS.766

When using these files, please cite: “Accurate Prediction of the Hydration Free Energies of 20 Salts through Adaptive Force Matching and the Proper Comparison with Experimental References”, Jicun Li and Feng Wang, J. Phys. Chem. B, 121, 6637, (2017)

The JPCB paper above reports the final parameters for this ionic models.

The citation that lays the foundation of the procedure for developing the MP2 based ionic potentials are
“Pairwise-additive Force Fields for Selected Aqueous Monovalent Ions from Adaptive Force Matching”, Jicun Li and Feng Wang*, J. Chem. Phys., 143, 194505 (2015).

For Na⁺, it will be important to be aware of the following work, where complication of the MP2 reference calculations is discussed.
“The Effect of Core Correlation on the MP2 Hydration Free Energies of Li+, Na+, and K+”, Jicun Li and Feng Wang, J. Phys. Chem. B, 120, 9088 (2016).

CO₂ potential developed by force-matching Local MP2.

Note that both the nbb model and the non-nbb model are released. For GROMACS, however, there is no reason to use the nbb model. The nbb input file is provided for checking against other codes that you may prefer to use that does not support bond-bond coupling.

CO2-LMP2A(&-nbb)

When using this model, please cite: “Leveraging Local MP2 to Reduce Basis Set Superposition Errors: an Efficient First-principles Based Force-field for Carbon Dioxide”, Ying Yuan, Zhonghua Ma, and Feng Wang*, J. Chem. Phys., 151, 184501 (2019)

Potentials for hydrated methane, ethane, methanol and ethanol.

Gromacs input files for

When using these models, please cite:“Accurate MP2-based force fields predict hydration free energies for simple alkanes and alcohols in good agreement with experiments”, T. Ryan Rogers and Feng Wang*, J. Chem. Phys., 153, 244505 (2020)

Gromacs input files for

Note there is no real reason to use the LMP2 based model for 1-4-butanediol. Please see discussion in our paper. (see below) The B3LYP-D3(BJ) based 1-4-butanediol has much better performance.

When using these models, please cite:“Determining the Hydration Free Energies of Selected Small Molecules with MP2 and Local MP2 Through Adaptive Force Matching”, Dong Zheng, Ying Yuan, and Feng Wang*, J. Chem. Phys., 154, 104113 (2021)

Gromacs input files for dilute aqueous solutions of the following solutes in BLYPSP-4F water developed based on B3LYP-D3(BJ) reference.