H-ULLAC, an integrated computer package for atomic processes in plasmas

We describe HULLAC, an integrated code for calculating atomic structure and cross sections for collisional and radiative atomic processes. This code e volved and has been used over the years, but so far, there was no coherent, comprehensive, and in-depth presentation of it. It is based on relativisti c quantum mechanical calculations including configuration interaction. The collisional cross sections are calculated in the distorted wave approximati on. The theory and code are presented, emphasizing the various novel method s that has been developed to obtain accurate results very efficiently. In p articular we describe the parametric potential method used for both bound a nd free orbitals, the factorization-interpolation method applied in the der ivation of collisional rates, the phase amplitude approach for calculating the continuum orbitals and the N-JGRAF graphical method used in the calcula tion of the angular momentum part of the matrix elements. Special effort ha s been made to insure the simplicity of use, which is demonstrated in an ex ample. (C) 2001 Elsevier Science Ltd. All rights reserved.