The suboption VELOCITIES will result in a restart from both, ionic and wavefunction velocities. In special cases, this is not the desired behavior. Using the additional keyword QUENCH the read velocities can be set back to zero. This will be most likely used for wavefunctions with QUENCH ELECTRONS. Another possibility is to reoptimize the wavefunction at the start of a molecular dynamics simulation. This is achieved with the keywords QUENCH BO.
For performance reasons the writing of the restart file should be done only occasionally. This might cause problems if the simulation was terminated incorrectly. Several hundreds or thousands of simulation steps might be lost. For this reason CPMD writes a special output file GEOMETRY after each molecular dynamics step. Together with a normal restart file this allows to start the simulation form the last ionic configuration and velocities. To achieve this another suboption GEOFILE has to be added to the RESTART keyword. After reading the positions and velocities of the ions from the restart file, they are also read from the GEOMETRY file and overwritten.
Special restarts to be used with the keywords TDDFT and VIBRATIONAL ANALYSIS are discussed in the sections covering that type of simulations.