Dft Studies of Fluid-Minerals Interactions At the Molecular Level: Examples and Perspectives

The scope of applications of first-principle theoretical chemistry methods has been vastly expanded over the past years due to the combination of improved methods and algorithms for solving the polyelectronic Schrödinger equation with exponential growth of computer power available at constant cost (the so-called Moore law). In particular, atomistic studies of solid-fluid interfaces are now routinely producing new qualitative and quantitative insights into adsorption, surface speciation as a function of the prevailing chemical potentials, and reactivity of surface species. This approach is currently widely exploited in the fields of heterogeneous catalysis and surface physics, and so far to a lesser extent for geochemical purposes, although the situation is rapidly evolving. Many fundamental issues of fluid-minerals interaction phenomena can indeed be addressed ab initio with atomistic 3D periodic models of fluid-solid interfaces involving up to 200-300 unequivalent atoms. We illustrate this proposal with recent IFP results, some of which are of primary interest with respect to the manufacture of catalysts supports, but which also show some relevance for inorganic geochemical issues in the context of the sequestration of acid gases in subsurface porous rocks: - reactive wetting of boehmite AlOOH and morphology prediction; - acido-basic surface properties of a transition alumina; - hydroxylation and sulfhydrylation of anatase TiO2 surfaces. Through these examples, the performances of DFT and a variety of up-to-date modeling techniques and strategies are discussed

Dft Studies of Fluid-Minerals Interactions At the Molecular Level: Examples and Perspectives

The scope of applications of first-principle theoretical chemistry methods has been vastly expanded over the past years due to the combination of improved methods and algorithms for solving the polyelectronic Schrödinger equation with exponential growth of computer power available at constant cost (the so-called Moore law). In particular, atomistic studies of solid-fluid interfaces are now routinely producing new qualitative and quantitative insights into adsorption, surface speciation as a function of the prevailing chemical potentials, and reactivity of surface species. This approach is currently widely exploited in the fields of heterogeneous catalysis and surface physics, and so far to a lesser extent for geochemical purposes, although the situation is rapidly evolving. Many fundamental issues of fluid-minerals interaction phenomena can indeed be addressed ab initio with atomistic 3D periodic models of fluid-solid interfaces involving up to 200-300 unequivalent atoms. We illustrate this proposal with recent IFP results, some of which are of primary interest with respect to the manufacture of catalysts supports, but which also show some relevance for inorganic geochemical issues in the context of the sequestration of acid gases in subsurface porous rocks: - reactive wetting of boehmite AlOOH and morphology prediction; - acido-basic surface properties of a transition alumina; - hydroxylation and sulfhydrylation of anatase TiO2 surfaces. Through these examples, the performances of DFT and a variety of up-to-date modeling techniques and strategies are discussed

Lithium Coordination Sites in LixTiO2(B): A Structural and Computational Study

A combination of powder neutron diffraction and computational methods, based on density functional theory (DFT), have been applied to study the evolution of structure with Li content for LixTiO2(B) in bulk and nanowire form. LixTiO2(B) is a promising anode material for rechargeable lithium batteries. Three structures were identified, Li0.25TiO2(B), Li0.5TiO2(B), and LixTiO2(B), where x corresponds to the maximum Li content, 0.8 (bulk) and 0.9 (nanowires). Together the techniques demonstrate that at low lithium concentration (up to 0.25) the square planar lithium site at the center of the b axis channel (C site) is preferentially occupied. At higher concentration, (Li0.5TiO2(B)) the C site becomes unfavorable and the 5-coordinate A1 site is occupied, whereas at the highest Li content, both A1 and a further 5-coordinate site, A2, are occupied equally.</p