Energy and forces

Two of the most important quantities we are interested in are the total energy and the forces on the atoms. To get these quantities, we have to define a calculator and attach it to an ase.Atoms object so that ase knows how to get the data. After defining the calculator a DFT calculation must be run. Here is an example of getting the energy and forces from a CO molecule. The forces in this case are very high, indicating that this geometry is not close to the ground state geometry. Note that the forces are only along the x-axis, which is along the molecular axis. We will see how to minimize this force in Manual determination and Automatic geometry optimization with FHI-aims.