Ab Initio Atom-Atom Potentials Using CamCASP: Theory and Application to Many-Body Models for the Pyridine Dimer.

Area of Science:

• Computational chemistry
• Molecular modeling
• Quantum chemistry

Background:

• Developing accurate atom-atom potentials for organic molecules is crucial but computationally demanding.
• Explicit polarization terms are essential for many molecular systems but add complexity to potential generation.

Purpose of the Study:

• To describe a method for generating accurate, analytic atom-atom potentials from first principles using the CamCASP program.
• To develop distributed multipole models and many-body potentials for the pyridine system, including electrostatic, polarization, and dispersion interactions.

Main Methods:

• Utilizing the CamCASP suite for generating potentials with accurate electronic structure methods.
• Deriving long-range terms from monomer properties and determining short-range anisotropy via the iterated stockholder atom approach.
• Developing distributed multipole models and many-body potentials for pyridine and its dimer.

Main Results:

• The simplest generated potentials showed root mean square errors of ~0.6 kJ mol(-1) for pyridine dimers, outperforming empirical potentials.
• The most advanced model identified eight stable minima, four previously unreported.
• Systematically improving potential accuracy is achievable without substantial increases in generation time.

Conclusions:

• The CamCASP approach provides a robust and accurate method for generating first-principles atom-atom potentials.
• The developed potentials for the pyridine system demonstrate high accuracy and reveal new stable configurations.
• The methodology allows for systematic refinement of potential accuracy and complexity.