The CASTEP Transition State Search dialog allows you to set up and display the parameters that control the TS Search task, including the protocol to be used and the quality of the search.
CASTEP transition-state searches require a trajectory document (for example, an
.xtd file) as input. You will not be able to start a transition-state search run unless a suitable document is in scope.
When a transition state search is performed on a periodic system the unit cell is fixed.
Search protocol: Select the type of synchronous transit that will be performed from the dropdown list. Available options are:
Quality: Set the TS search convergence thresholds for the root mean square (RMS) forces on the atoms. The search will stop when this criterion is satisfied.
Five quality settings are available:
The value of the convergence threshold for each setting is given in the table below:
|RMS convergence (eV Å-1)||0.1||0.5||0.25||0.05||0.01|
RMS convergence: Specify the value, in eV Å-1, at which convergence is considered to take place in terms of the RMS of the gradients.
Max. number QST steps: Specify the maximum number of QST maximization cycles. If this number of cycles is reached, then the calculation will stop, even if the convergence criteria are not satisfied.
Optimize reactants and products: Specifies that the input structure for the reactant and product in a TS search calculation should be optimized to a local minimum. Selecting this allows the TS search to start from a "raw" trajectory, where the reactant and product structures have not already been optimized.
This choice may lead to reactant and product structures deviating substantially from the input structures, so it is recommended that you carefully check the final path.
Calculate partition functions: Specifies whether to calculate partition functions based on the Gamma-point dynamical matrix for the reactants, products, and the transition state. This data will be stored in the output 3D Atomistic Collection document.
This is not available unless Optimize reactants and products is checked.
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Synchronous transit methods
CASTEP Transition State Search task
Setting up a transition state calculation