In the context of first-principles BOMD, the separation of the forces into fast and slow components is not straightforward. In the CPMD package we have chosen to use different levels of electronic structure theory to decompose the forces. Typically, a "low" level density functional (e.g. GGA) is used to calculate the fast components of the nuclear forces, while the slow components are obtained as the difference between the forces obtained with a "higher" level functional (e.g. hybrid) and the "low" level forces,