It is possible to use different types of thermostats in CP2K by specifying them in the corresponding section of the input as mentioned here. But there is no mention of specifying the barostat type in the manual. And I couldn't find any mention of the type of barostat being used in CP2K for NPT simulations. So is it possible to use the Parrinello-Rahman barostat for NPT simulations in CP2K?
The barostat used by CP2K is the one developped by Glenn J. Martyna et al. J. Chem. Phys. 101, 4177 (1994).
The Parrinello-Rahman barostat is not implemented in CP2K.