  Complete modeling of radiative transfer in neutron star atmospheres is in
progress, taking into account the anisotropy induced by magnetic fields,
non-ideal effects and general relativity. As part of our modeling, we present a
novel atomic calculation method producing an extensive atomic data set
including energy values and oscillator strengths in the so-called Landau regime
($B > 4.7\times10^9Z^2$ G). Conventional atmosphere models for B=0 are not
applicable to typical field strengths of cooling neutron stars ($B
\sim10^{12}-10^{13}$ G), since an atom no longer keeps its spherical shape. The
elemental composition and the configuration of the magnetic field in the
atmosphere are presently unknown, so that atomic data must be produced for
ground and excited states of several ions as a function of magnetic field. To
accomplish this efficiently, we minimized the iterations in the Hartree
equation and treated exchange terms and higher Landau states by perturbation
methods. This method has the effect of reducing the computation time
significantly. Inclusion of higher Landau states gives us much more accurate
data for inner orbitals unlike other methods based on the adiabatic
approximation. While existing atomic data in the Landau regime are available
only for low $Z$ atoms, our method can be used in elements up to Fe with
sufficient accuracy to be of use for spectroscopic missions such as {\it
Chandra}, {\it XMM-Newton} and next-generation X-ray telescopes.
