External module function dS1 - used by mcdisp

In order to visualize spin fluctuations and to calculate neutron intensities in dipole approximation the external single ion module has to provide the transition matrix elements of the spin by the vector $S1$, which is given by: ${\rm S1}^s_{\alpha}=\sqrt{(p_--p_+)}\langle -\vert\hat S^s_{\alpha}-\langle \hat S^s_{\alpha}\rangle_{\mathbf H,T}\vert+\rangle$.

The format to be used is:

extern "C" int dS1(int & tn,double & T,Vector & Hxc,Vector & Hext,double * g_J,Vector & MODPAR,
char ** sipffilename,ComplexVector & S1,float & maxE, ComplexMatrix & est)

The meaning of the symbols follows exactly that of function dm1 and therefore not explained here.