Geometry Optimisation with CASTEP

There is an inital dip in the forces at around iteration 14 as some search direction is tried but this causes
an increase in the energy. Then there is a large increase in the forces (presumably due due dimer
attraction) accompanied by a large energy gain which are due to dimerisation. There is then a small peak
in the forces and the energy at about iteration 24 as the energy barrier to asymmetric dimerisation is
overcome.
In summary, this example has illustrated the use of constraints upon atomic positions and has also looked
at hydogen passivation and the variation of both the number of layers of atoms and the thickness of the
vacuum gap as ways to deal with aperiodic supercell configurations such as surfaces.
Next: References Up: Geometry Optimisation with CASTEP Previous: A Variable Cell calculation
2005-04-03