The CASTEP module allows you to perform first-principles quantum mechanical calculations in order to explore the properties of crystals and surfaces in the solid state. CASTEP can currently perform several different tasks:
Each of these calculations can be set up so that it generates specified chemical and physical properties. An additional task, known as a properties calculation, allows you to restart a completed job to compute additional properties that were not calculated as part of the original run.
There are a number of steps involved in running a CASTEP calculation, which can be grouped as follows:
In the case of a transition-state search, a 3D Atomistic Trajectory document containing a reaction sequence is required as the input document. You should define the structures of the reactants and the products in two separate 3D Atomistic documents via the methods listed above and then use the Reaction Preview tool to generate the trajectory.
CASTEP can only be used to perform calculations on 3D periodic structures. If you wish to study a molecular system using CASTEP, you will need to construct a supercell to use as the input structure.
CASTEP performance can be greatly increased if the symmetry of the structure is taken into account. CASTEP offers an option of finding and using the symmetry automatically if the input structure is described as having a P1 symmetry. This option is particularly relevant for calculations on molecular crystals and crystal surfaces, since these structures are typically created as P1 (or p1) systems. Automatic conversion to a higher symmetry structure will honor all atomic properties that are relevant to the current CASTEP settings, such as constraints and electronic configuration.
The time required for a CASTEP calculation increases with the cube of the number of atoms in the system. Therefore, it is recommended that you use the smallest primitive cell description of your system whenever possible. Select Build | Symmetry | Primitive Cell from the menu bar to convert to a primitive cell.
To select a CASTEP task
The following topics provide more detail about the various steps involved in setting up and running a CASTEP calculation:
CASTEP tutorials are available to lead you through the various procedures in a step-by-step manner.
Theory in CASTEP
Dialogs in CASTEP