Caracal: A Versatile Ring Polymer Molecular Dynamics Simulation Package.

Area of Science:

• Computational Chemistry
• Molecular Dynamics
• Chemical Physics

Background:

• Simulating molecular systems requires accurate potential energy surfaces (PES) and efficient dynamics methods.
• Ring polymer molecular dynamics (RPMD) is a powerful technique for calculating reaction rates.
• Existing software packages may lack integrated capabilities for both PES generation and advanced dynamics simulations.

Purpose of the Study:

• Introduce Caracal, a new open-source program package for molecular simulations.
• Provide an all-inclusive approach combining RPMD with various PES methodologies.
• Facilitate chemical reaction rate calculations and the study of liquid systems.

Main Methods:

• Utilizes ring polymer molecular dynamics (RPMD) for simulations.
• Implements quantum mechanically derived force field (QMDFF) and empirical valence bond (EVB)-QMDFF methods for PES construction.
• Employs biased sampling techniques (umbrella sampling, recrossing calculations) for rate constants.
• Supports polymerization of QMDFFs for liquid system descriptions.

Main Results:

• Caracal offers a powerful RPMD implementation with chemical reaction rate calculations.
• The package integrates easy-to-set-up PES methodologies, including QMDFF and EVB-QMDFF.
• Demonstrates the capability to classify reaction mechanisms and obtain RPMD rate constants.
• Shows potential for describing liquid systems through polymerized QMDFFs.

Conclusions:

• Caracal provides a comprehensive and user-friendly platform for advanced molecular simulations.
• The integration of RPMD and flexible PES methods enhances the study of chemical reactions.
• The software package is well-suited for both gas-phase reaction dynamics and condensed-phase system analysis.