Workshop CECAM "Atomistic Simulations in Earth Sciences" - June 17, 2015 to June 19, 2015 - UPMC

Bât. Esclangon, Amphi Durand

Organisers

• Rodolphe Vuilleumier (Ecole Normale Supérieure, Paris, France)
• Guillaume Ferlat  (IMPMC - UPMC)
• A. Marco Saitta (IMPMC - UPMC)

Description 

Although the time and length scales involved in Earth Sciences span large order of magnitudes, molecular processes play a key role in many situations: metal complexation in water, acid-base processes, dissolution of volatiles, phase transformations etc. Understanding these processes is crucial to address questions like the carbon budget in the Earth mantle and the possibility of geochemical storage, ore formation and localization, mechanisms and signatures of volcanic eruptions, composition of the deep Earth interior and its dynamics… With the recent development of high-pressure experiments, many such processes are nowadays studied at the molecular level using chemical-physics tools such as EXAFS, XANES, Raman spectroscopy, x-ray and neutron diffraction etc. In this context, computer simulation at the molecular level plays an increasing part in the study of matter in these mild to extreme conditions. However, if the potential benefit of computer simulations to study atomic processes at conditions hard or even impossible to reach experimentally is clear, huge challenges remain to be tackled because of the chemical complexity of the systems and the several different time and length scales involved. For example, if we consider hydrothermal solutions, some solute, ions in particular like chlorine, may be buffered by mineral assemblages, some not. Similarly, minor species can play a crucial role in metal solubility because of the strong interaction with it. It is then important to sample not only the configuration space, but also the chemical space. Spectroscopies, in particular x-ray absorption, are essential for comparing the proposed chemical models to experiments and constrain the description of local environments. However, the next step consists in calculating thermochemical properties themselves.

The scope of the workshop is to bring together scientists from different communities (physics, chemistry, and Earth sciences), sharing a common interest in computational research in the broad Earth sciences field, such as, but not restricted to, the chemical, structural, dynamical and thermodynamic properties of geological fluids and minerals, the study of atmospheric chemistry, the modeling of the interior of Earth, of planets and of satellites. Participants will be invited to address the following questions 1) What mechanism drive speciation in geochemical environment? What is the role of composition? Can we determine the chemical potential of the different constituents? How spectroscopy helps constraining the system? 2) What are the necessary ingredients (definition of system, force-field…) to compute thermochemical quantities such as solubility, formation constants, pKa, oxydo-reduction potential? How can we define a reference for defining these quantities? 3) Can we address specific quantities like pCO2, fO2 that are defined for geochemical systems? Are new algorithms needed? 4) How can we bridge time-scales for describing slow processes like transport, mineralization and reversely alteration of minerals, phase equilibria? The workshop will allow experts in the field, from ab initio methods, to classical molecular dynamics, coarse-grained models and multi-scale techniques, to discuss the state of the art, both in terms of results and methods, and will stimulate novel ideas to undertake the challenges of this field, and to develop new interdisciplinary collaborations.

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