Capabilities of quantum-mechanical methods

In this final chapter, an attempt is made to provide an overview of the capabilities of quantum-mechanical methods at the present time, and to highlight the needs for future development and possible future applications of these methods, particularly in areas related to mineral structures, energetics, and spectroscopy. There is also a brief account of some new areas of application, specific directions for future research, and possible developments in the perception and use of quantum-mechanical approaches. The book ends with an epilog on the overall role of theoretical geochemistry in the earth and environmental sciences. 

The quantum-mechanical description of minerals containing transition metals is at a less advanced stage. The accuracy of simple Hartree-Fock-Roothaan methods has not been fully determined for such systems. Local-density-functional methods have been successful for calculating the structural properties of high-symmetry materials, but excitation energies are still poorly reproduced. Local-density-functional cluster calculations have so far been restricted mostly to model potentials (e.g., muffin-tin potentials) so that their full power has not been utilized. We need to determine the accuracy and efficiency of Hartree-Fock-Roothaan (or Har- 

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The interaction between computational chemistry and experimental magnetic resonance spectroscopies is increasing at a fast pace in recent years. This parallels a more general trend of successful synergic interactions between experimentalists and computational chemists based on the capability of quantum mechanical methods to provide reliable estimates for a large number of spectroscopic parameters. 

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