Mineral surface quantum-mechanical calculations

To date, our understanding of the speciation of metals in hydrothermal fluids and on mineral surfaces has been based largely on the classical Born model. It is clear that we can now go wed beyond this approach and develop an atomistic picture of aqueous solutions based on either quantum mechanics or classical simulations. Classical simulations using simple pair potentials appear to give a reliable picture of of alkali and alkaline earth halide solutions. Some transition metals (such as Zn, Cu and Mn ) can also be treated at this level. Systems where there is hydrolysis and proton transfer, however will require either dissociatable water models or must be done using quantum mechanical calculations. Quantum mechanical calculations are also needed to understand... 

The greatest shortcoming of quantum mechanical calculations on metal complexes and mineral surfaces is an inadequate description of solvation. To that end, dielectric continuum models are still of use, but only to describe the long-range solvation effect. With increasing computational power, moreover, the application of plane-wave pseudopotential based ab initio molecular dynamics will allow us to explicitly treat bulk solution effects from first-principles calculations on large systems. 

It is well known that the flotation of sulphides is an electrochemical process, and the adsorption of collectors on the surface of mineral results from the electrons transfer between the mineral surface and the oxidation-reduction composition in the pulp. According to the electrochemical principles and the semiconductor energy band theories, we know that this kind of electron transfer process is decided by electronic structure of the mineral surface and oxidation-reduction activity of the reagent. In this chapter, the flotation mechanism and electron transferring mechanism between a mineral and a reagent will be discussed in the light of the quantum chemistry calculation and the density fimction theory (DFT) as tools. 

Lasaga, A.C., and Gibbs, G.V., Quantum mechanical potential surfaces and calculations on minerals and molecular clusters, I. STO-3G and 6-31G results, Phys. Chem. Miner., 16, 29, 1988. 

Lasaga, A. C., and G. V. Gibbs (1987). Applications of quantum mechanical potential surfaces to mineral physics calculations. Phys. Chem. Mineral. 14, 107-17. 

Improvements of spectroscopic techniques based on synchrotron radiation will allow new probes of hydrothermal solutions and mineral surfaces. However, the interpretation of this data is greatly aided by first-principles calculations of bond lengths and spectroscopic properties. Discrepancies between theory applied to gas-phase molecules and experimental data on aqueous complexes can provide an indirect probe of solvation. The computational technology is sufficiently well developed that there is no excuse for an experimentalist not to employ quantum mechanical and classical simulations to help interpret experimental results. 

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