Keywords
To perform a geometry optimisation set the task parameter
The convergence criteria have the following default values, each of which can be set independently.
geom_energy_tol: Tolerance on energy change between iterations (default: 2.0e-5 eV)geom_force_tol: Tolerance on maximum force on each atom (default: 0.05 eV/ANG)geom_stress_tol: Tolerance on maximum stress on cell (default: 0.1 GPa)geom_disp_tol: Tolerance on change in atom positions between iterations (default: 0.001: Ang)geom_max_iter: Maximum number of iterations (default: 30)
It is possible to change the optimisation method, and to choose a preconditioner.
geom_method : LBFGS (default), BFGS, TPSD, DAMPEDMD, FIRE
geom_preconditioner : EXP / FF / ID # EXPonential, Force Field, Identity (default)
It is useful to set the following two parameters in a geometry optimisation. These will cause CASTEP to write a new cell/cif file with the final optimised coordinates