1.8 How do I plot the phonon dispersions?

Use what='scf_disp'. See example04. In this case you have to prepare an input for the ph.x code that must be called ph_control. The required information in this input is the q-point mesh on which the dynamical matrices are computed and the name of the files where the dynamical matrices are written. See the ph.x guide if you need information on this point. At the end of the run, the phonon dispersions are found in a file called by default output_disp.g1.ps, a name that can be changed in the THERMO_PW input. The vibrational density of states is found in a file called by default output_dos.g1.ps, which can also be changed in the THERMO_PW input.