- CP-dynamics with Simulated Annealing:

One can actually perform a wavefunction optimization by running a CP-dynamics with all atom positions frozen and then gradually removing kinetic energy from the fictitious degrees of freedom by multiplying velocities with a factor (in the example here it is set to 0.9, so 10% of the kinetic energy will be removed in every step). Particularly for systems, that are very difficult to converge or where the ``fast'' methods like DIIS or PCG converge to the wrong state, this may be the only way to get to the (desired) ground state. To do this a few more modifications of the input file are needed. The &CPMD section becomes:

&CPMD
 MOLECULAR DYNAMICS CP
 ANNEALING ELECTRONS
   0.90
 MAXSTEP
   200
 EMASS
  800.0
 TIMESTEP
   6.0
&END

and we need to add to the &ATOMS section the following:

CONSTRAINTS
  FIX ALL ATOMS
END CONSTRAINTS

Note: Unlike with the regular wavefunction optimization methods there is no automatic stop when the wavefunction is converged, so the number of steps has to be either overestimated or the run restarted several times. Also, the annealing factor has to be chosen carefully. If it is too close to 1.0, it will take a very long time to converge, but if it is too small (0.90 is quite aggressive), the calculation will get ``frozen out'' before it fully reaches the minimum.