3.16 what='scf_magnetoelectric_tensor'

With this option the code calculates the magnetoelectric tensor ( 13#13 8#8 = 1, 3,12#12 = 1, 3 ) of the solid. It generates a mesh of ngeo_b values of the magnetic field for each direction required by the magnetic point group and after converging it computes the Berry phase polarization of the system. Finally it makes the derivatives of the polarization with respect to the magnetic field.

For each magnetic field, it relaxes the ions to their equilibrium positions when frozen_ions=.FALSE. or keeps them in the original positions when frozen_ions=.TRUE..

Therefore the resulting magnetoelectric tensor contains both the electronic and ionic contribution in the first case, or only the electronic contribution in the second case. When using frozen_ions=.TRUE. it is important to calculate the equilibrium atomic positions and not use those strained from the thermo_pw input using the flag ltau_el_cons_from_file (please check the use of this flag in the what='scf_elastic_constants' option.

To control the grid of magnetic fields used please see the what='scf_magnetic_susceptibility' option.