Chemical Reactions
Q-Chem provides a suite of tools for calculating and analyzing potential energy surfaces to assist in the understanding of chemical reactions.
Geometry Optimization
- Optimization in automatically generated internal coordinates
- Constrained optimization
- L-BFGS algorithm for large QM/MM optimizations
- Hessian-free methods for stationary point characterization
Potential Energy Surface Scans
- Both relaxed and unrelaxed PES scans
- Support for scanning over one or two independent geometric variables

Transition Structure Search
- All geometry optimization features are available for transition structure optimization
- The Freezing String Method (FSM) automates the search for candidate transition structures
- Hessian-free methods automatically launched from FSM
- Improved dimer method
Intrinsic Reaction Coordinate
- Automatically determines which minima are connected to a given transition structure
- Reaction paths can be followed in either Z-matrix, Cartesian or mass-weighted Cartesian coordinates
Minimum Energy Crossing Points

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