| 1. |
- Ferreira de Lima, Guilherme, et al.
(författare)
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X-ray Absorption Near-Edge Spectroscopy Calculations on Pristine and Modified Chalcopyrite Surfaces
- 2018
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 122:35, s. 20200-20209
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Tidskriftsartikel (refereegranskat)abstract
- Understanding chemical modifications on the chalcopyrite surface is an important issue to improve hydrometallurgical processes to recover copper from the mineral. X-ray absorption near-edge spectroscopy (XANES) can be used for this task, but the interpretation of the spectrum and the correlation with chemical changes in the first atomic layers are not straightforward. The present study demonstrates the potential of combining spectrum measurements with theoretical X-ray spectrum simulations to elucidate the chemistry behind weathering of important classes of minerals. We simulated the S and Fe K-edge XANES spectrum for pristine and modified chalcopyrite surfaces using periodic DFT calculations and the transition-potential model. The calculated S K-edge XANES spectra are in good agreement with experimental data and the peaks were attributed using the density of states. The simulated Fe K-edge XANES spectra do not reproduce all features observed experimentally. The effect of surface changes due to reconstruction, hydration, and oxidation on the spectrum was analyzed. Our results show that the S K-edge XANES spectrum is more sensitive to surface modifications than the Fe K-edge XANES spectrum, and this sensitivity could be used to follow the evolution of the surface.
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| 2. |
- Lourenco, Maicon Pierre, et al.
(författare)
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Accurate SCC-DFTB Parametrization for Bulk Water
- 2020
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Ingår i: Journal of Chemical Theory and Computation. - : American Chemical Society (ACS). - 1549-9618 .- 1549-9626. ; 16:3, s. 1768-1778
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Tidskriftsartikel (refereegranskat)abstract
- The SCC-DFTB repulsion parameters based on the material science set (matsci) were redesigned to describe the structure and dynamic properties of bulk liquid water. The iterative Boltzman inversion (IBI) approach was applied by simultaneously correcting the O-H and O-O SCC-DFTB repulsion energy contribution to develop the new water-matsci and water-matsci-UFF set of parameters. The water-matsci parameters provide O-O and O-H radial distribution functions in excellent agreement with available state-of-the-art experimental data. The parametrization is applied to compute binding energies of a set of water clusters with 2-10 molecules and compared to other DFTB parameters and reference data. The self-diffusion coefficients of ambient and supercooled (254 K) water have been estimated and compared to other SCC-DFTB calculated values and experiment. The performance of the new parameters for describing the density of ambient water and reactions involving water dissociation into H3O+ and OH-, the self-diffusion coefficient, and neutralization energy were investigated. Finally, we show that the new parametrization can be reliably applied to adsorption of water on the mineral pyrite by combining the new water-matsci parameters with the available matsci set of parameters for pyrite. This opens opportunities for investigating materials and phenomena of increasing complexity involving water.
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