Jaguar Optimizations and Scans

For Hartree-Fock, LMP2, and DFT calculations in gas phase or in solution, Jaguar can use calculated analytic gradients to optimize the molecular geometry to a minimum-energy structure or a transition state. The minimum-energy structure can be the ground state or an excited state. For excited states that have a different symmetry (spatial or spin) from the ground state, you can use the usual HF, LMP2, or DFT method to find the lowest state of that symmetry. Attempting to optimize to a state that is not the lowest state of a given symmetry usually collapses to the lowest state. However, for an excited state of the same symmetry as the ground state, you can use TDDFT to find the minimum. See Introduction to Geometry Optimizations, Functionals, and Basis Sets for a tutorial exercise.

In addition to locating stationary points, Jaguar can calculate points along one or more coordinates, with or without optimizing the other coordinates. These scans include intrinsic reaction coordinate (IRC) and minimum energy path (MEP) scans as well as geometry scans of specified coordinates.

There are five tasks in the Task Tool that support optimizations and scans:

• Optimization1 Keyword igeopt = 1 in the gen section.
• Relaxed Coordinate Scan
• Rigid Coordinate Scan
• Transition State Search2 Keyword igeopt = 2 in the gen section.
• Reaction Coordinate3 Keyword irc = 1 in the gen section.

Settings for each of these tasks can be made in the tabs in the panel. The details are in the panel topics:

• Optimization Panel
• Relaxed Coordinate Scan Panel
• Rigid Coordinate Scan Panel
• Transition State Search Panel
• IRC Panel

The topics listed below describe the optimization and scan features. Footnotes indicate the Jaguar input file keywords that correspond to particular GUI settings.