3.15 what='scf_magnetic_susceptibility'

With this option the code calculates the magnetic susceptibility ( 11#11 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 symmetry and computes the magnetization.

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.. Finally it fits the magnetization with a linear or cubic polynomial and extracts the derivative with respect to the field.

The input variables that control this option are:

frozen_ions: if .TRUE. the magnetic susceptibility is calculated 
             keeping the ions frozen in the input configuration. 
             Default: logical .FALSE.
ngeo_b: the number of magnetic fields configurations used 
             for each direction. 
             Default: integer 4
delta_b: the interval of magnetic field between two 
             geometries. The magnetic field is given in Rydberg units. 
             Default: real 0.002
dm:          A vector of size dm is added to the starting magnetization
             vector in the direction of the magnetic field to break symmetry.
             Starting_magnetization goes from 0.0 to 1.0 so this dm is
             in these units. We use the same dm for all atoms with nonzero
             starting magnetization. Moreover only the initial angles 
             of the magnetization are changed not its magnitude.
             Default : real 0.002

Number of tasks for this option: ngeo_b times the number of directions that need to be studied.