- Move ions into new positions using geometry optimisation algorithm
- Optimise electronic configuration using conjugated gradients method
- Compare total energy with previous configurations and check if forces within tolerance limits
- If structure not optimised start at (1) and generate new set of ionic positions

This cycle is performed until the forces fall within the tolerance limit and the energy should then be a local
minimum.

What types of system can this be applied to? In theory CASTEP can geometry optimise most bulk systems in a wide range
of materials such as semiconductors, ceramics, metals, minerals and zeolites. It can also look at defects such as surfaces.
The main restriction is the amount of computational resources available to the user. Calculations scale with the cube of
the number of atoms included. More about this in the discussion of supercells.