MAGIC: an integrated computational environment for the modelling of heavy-atom chemistry

The nuclear industry has enormous challenges to address in understanding it s waste products and their safe disposal. It is extremely expensive and dif ficult to work with such waste products. As computational chemistry has mad e so many advances in the last 30 years, the question arises as to whether it can start to answer some of the basic questions. It was in this context that British Nuclear Fuels pie approached the quantum chemistry group at th e University of Cambridge. After initial considerations, it was decided to write an entirely new quantum chemistry package to address these fundamenta l problems. The MAGIC Il program has been written to model as accurately as possible the properties of heavy-atom (in particular, actinide) complexes in realistic environments. Major requirements were the need to include rela tivistic effects for which several investigations have been carried out by quantum chemists in recent years. A severe difficulty is the high angular m omentum of the occupied orbitals in the actinides. It was also believed tha t it was very important to include the effects of electron correlation. Aga in much progress has been made by quantum chemists with this problem. There fore this code was written to take into account all these advances in a sim ple enough way that calculations on realistic systems are possible. The pro gram is the result of a collaboration between British Nuclear Fuels pie and the University of Cambridge. The program has been developed with a view to making the implementation of new ideas as straightforward as possible. Hen ce, the code has a simple modular structure. Individual modules may of cour se be combined in a script to run more complicated procedures, such as a se lf-consistent field (SCF) procedure. The aim of such an approach is to maxi mize the time spent in the science compared with that spent interfacing wit h the computer code. For the end user a simple graphical user interface thr ough Cerius(2) is provided. Standard features of the input may be selected easily from individual menus for each module. It is also possible to access more advanced features. Comprehensive help facilities are available within the interface. Use of the visualization tools helps not only to see the re sults of calculations on large molecules more clearly, but also to present them in a concise and clear way. The program has been developed on an SG wo rkstation, but it has been extended to run in parallel on a Gray T3E. This paper is the basic paper which describes in detail the philosophy, science and implementation of the MAGIC project. At the end, sample calculations ar e reported. Furthermore suggestions are made about how this program may, ev en at this stage, be used to address problems with actinides in the nuclear industry. In order to place the development of the MAGIC project in contex t and to make adequate recognition of the contribution of others, this arti cle contains considerable material of a review nature, a brief history of t he development of quantum chemistry and density function theory, the treatm ent of core electrons and relativistic effects, the evaluation of integrals , the treatment of solvent effects and the convergence of the SCF iteration s. All are written with calculations on actinide complexes as the ultimate goal.