3.13 what='scf_polarization'

With this option the code calculates the spontaneous polarization. It makes a self-consistent calculation followed by three Berry phase calculations in which the polarization is calculated in the directions of the direct lattice vectors and prints the spontaneous polarization in Cartesian coordinates. Please note that the zero of the polarization is not subtracted. frozen_ions=.TRUE. require also a previous what='scf' calculation where the atomic positions of the equilibrium configuration are calculated and written on file. ltau_el_cons_from_file=.TRUE. must be used.

The input variable that controls this option is:

nppl: the number of k points per string. In the perpendicular 
      plane the number of k points is that given as input 
      of the pw.x code.
      Default: integer 21