Calculations of Delbruck scattering to all orders in αZ

We present a theoretical method to calculate Delbruck scattering amplitudes. Our formalism is based on the exact analytical Dirac-Coulomb Green's function and therefore accounts for the interaction of the virtual electron-positron pair with the nucleus to all orders, including the Coulomb corrections. The numerical convergence of our calculations is accelerated by solving the radial integrals that are involved analytically in the asymptotic region. Numerical results for the collision of photons with energies 102.2 and 255.5 keV with bare neon and lead nuclei are compared with the predictions of the lowest-order Born approximation. We find that our method can produce accurate results within a reasonable computation time and that the Coulomb corrections enhance the absolute value of the Delbruck amplitude by a few percent for the studied photon energies.