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Recent NWChem developments enhance the COSMO solvation model with a new cavity construction and improved charge correction. This leads to accurate dielectric solvation energies and promising equilibrium predictions.

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Area of Science:

  • Computational chemistry
  • Quantum chemistry
  • Theoretical chemistry

Background:

  • The COSMO (COnductor-like Screening MOdel) solvation model is crucial for simulating chemical processes in solution.
  • Accurate implementation of solvation models is essential for reliable computational chemistry predictions.
  • Previous implementations may have limitations in cavity construction and surface charge handling.

Purpose of the Study:

  • To present recent advancements in the COSMO solvation model implementation within the NWChem computational chemistry software.
  • To introduce a novel cavity construction method based on the solvent-excluding surface (SES).
  • To improve the accuracy and robustness of charge correction schemes in the COSMO model.

Main Methods:

  • Implementation of a new cavity construction algorithm using the GEPOL method and solvent-excluding surface (SES).
  • Development of a procedure to merge close surface segments, mitigating numerical artifacts.
  • Review and enhancement of methods for correcting outlying surface charges.
  • Computation of dielectric solvation energies for a diverse set of ~100 molecules.
  • Comparison of NWChem results with GAMESS using the double-cavity method.

Main Results:

  • The new NWChem implementation achieves excellent agreement with reference methods for dielectric solvation energies.
  • Mean unsigned deviations of approximately 0.15 kcal/mol were obtained with simplified correction schemes.
  • Predictions of vapor-liquid and liquid-liquid equilibria using a COSMO-SAC variant showed highly promising results.
  • The improved methods effectively handle surface charge complexities and reduce numerical artifacts.

Conclusions:

  • The enhanced COSMO implementation in NWChem provides accurate and reliable solvation energy predictions.
  • Simplified correction schemes in NWChem can achieve high accuracy comparable to more complex methods.
  • The advancements facilitate more precise simulations of chemical behavior in solution and phase equilibria.