### External module function spindensity_coeff - used by densplt, spins, display_density,display_densities

In order to calculate spindensities the following function has to be present in the module file *.so:

extern "C" void spindensity_coeff(Vector &aSlm, int & xyz, double *T,Vector &Hxc,
Vector & Hext,double *gJ,Vector &MODPAR,char **sipffilename,ComplexMatrix & Icalc_parstorage);


Note for windows users with MINGW the declaration should be extern "C" __declspec(dllexport) void spindensity_coeff(...).

The meaning of the symbols is as follows:

  on input
xyz         direction index 1,2,3 = x,y,z (component for the spindensity vector to be calculated)
T           temperature[K]
Hxc        vector of exchange field [meV] (can be n-dimensional, for a set of n operators)
Hext      external magnetic field [T]
gJ          Lande factor
MODPAR      Vector with Parameters  read in single ion property file
sipffilename    file name of the single ion parameter file
Icalc_parstorage parameter matrix (initialized by Icalc_parameter_storage_matrix_init)
it should/may contain any information, e.g. population numbers of the
states (imaginary part of row 0)
and eigenvalues (real part of row 0) with values set by the most recent call
for this ion (making use of this matrix is optional)
on output
aSlm         Output single ion moments =expectation values of
coefficients of Zlm R^2(r) at a given temperature T and
effective field H


The module function must perform the following tasks:

1. calculate the coefficients of in the expansion of the spin density vector The output Vector alm(1,...,49) should contain in the following order (lm): 00,1-1, 10,11, 2-2, 2-1,20,21,22, 3-3, 3-2, ...,65,66
2. if all quantities should be evaluated assuming that all Boltzmann probabilities are zero except for the state number , for which the probability .

Martin Rotter 2017-01-10