  The PAW method has been used to compute the iron L$_{2,3}$ edges of x-ray
absorption spectra (XAS) and x-ray magnetic circular dichroism (XMCD) of the
spin-crossover Fe(phen)$_{2}$(NCS)$_{2}$ molecule when adsorbed on Cu(001)
surface and in the gas phase, for both the high spin (HS) and low spin (LS)
states. It is found that the calculated XAS and XMCD with the static core hole
or the Slater transition state half hole are in less good agreement with
experiment than those using the so called initial state. This disagreement is
due to the reduction of the iron spin magnetic moment caused by the static
screening of the core hole by the photo-electron. The L$_{2,3}$ XAS formula is
found to be directly related to the unoccupied $3d$ density of states (DOS),
and hence the symmetry broken $e_g$ and the $t_{2g}$ iron DOS are used to
explain the XAS and XMCD results. It is demonstrated that the dependence of the
HS XMCD on the direction of incident x-ray circularly polarized light with
respect to the magnetization direction can be used to determine the iron
octahedron deformation, while the XMCD for various magnetization directions is
directly related to the anisotropy of the orbital magnetic moment and the
magneto-crystalline energy. It is also shown that the magnetic dipole moment
$T_z$ is very large due to the strong distortion of the iron octahedron and is
necessary for an accurate determination of the sum rule computed spin magnetic
moment.
