Computational modelling of (geo)materials makes use of first-principles or ab initio calculations, that is, quantum mechanical computations based only on elemental physical constants of nature such as the electron charge, atomic masses, etc., with the main objective of understanding physical and chemical properties of a variety of materials studied because of their fundamental interest, their relevance in technological applications and their importance for Earth and planetary modelling. Over the next 5-year period (2017-2022), the general goal of these investigations will be to increase our knowledge in the mineral physics, geophysics and materials science. In the geosciences, the understanding of Earth materials in terms of their atomic arrangements, structural bondings, chemical compositions, magnetic state, elastic coefficients, etc. will provide insights into the complex interactions between our surface environment and the deep planet. Moreover, the joint effort between the theoretical/computational modelling with the experimental part will advance a more accurate portrayal of our planet and others. Thus, our research will address the following questions:
- How does the elasticity of different iron-bearing olivine- and spinel-type minerals compare to each other as predicted by first-principles?
- How does cation disorder influence the physical properties of minerals belonging to the spinel, olivine and perovskite families?
- How does the electronic state of iron and other magnetic ions change in different minerals at high pressures –and what is the effect of such changes on the physical properties of the minerals?
- How are thermal and electrical conductivities altered by pressure, temperature, and composition?
From the materials science point of view, the identification of precise features that controls the functionalities of complex materials for specific technological applications is the subject of intensive experimental, theoretical and computational research. In particular, within the area of “Georesources” using first-principles calculations, new functional materials and alternative energy sources can be designed and characterized, with the potential to become substitutes to natural resources in the long term.
Kontakt
Prof. Dr. Maribel Núñez-Valdez
Fe2+ and Fe3+ are the most abundant transition metal ions (3dN-ions) in minerals constituting the Earth’s mantle. Both Fe2+ (d6-) and Fe3+ (d5-electronic configuration) may undergo transitions from the high-spin (HS) to low spin (LS) state at pressures and temperatures expected in the Earth’s mantle. Such pressure-induced spin transitions have been predicted in 1960 by W. S. Fyfe. This phenomenon would lead to marked changes in geophysically important properties, such as elasticity and conductivity, and also to a different geochemical behavior, such as element partitioning. Therefore, this transition may have major influence on the Earth’s structure and dynamic.
The HS-LS transition of iron on the electronic energy levels of Fe2+ and Fe3+ can best be seen in optical absorption spectra but the properties are controversially discussed. To get a clear picture of how the optical spectra of oxygen-based minerals transform during the spin transition we collect spectra as a function of pressure from a material with a simple and intense spectrum of the electronic transition of Fe2+ to trace the HS-LS transition by optical spectroscopy and get better insight in these fundamental processes. The material of our choice are minerals of the triphylite-lithiophilite series.
Taran, M. N., Núñez Valdez, M., Efthimiopoulos, I., Müller, J., Reichmann, H.-J., Wilke, M., Koch-Müller, M. (2019): Spectroscopic and ab initio studies of the pressure-induced Fe2+ high-spin-to-low-spin electronic transition in natural triphylite–lithiophilite. - Physics and Chemistry of Minerals, 46, 3, 245-258.
https://doi.org/10.1007/s00269-018-1001-y
Núñez Valdez, M., Efthimiopoulos, I., Taran, M., Müller, J., Bykova, E., McCammon, C., Koch-Müller, M., Wilke, M. (2018): Evidence for a pressure-induced spin transition in olivine-type LiFePO4 triphylite. - Physical Review B, 97, 18, 184405.
https://doi.org/10.1103/PhysRevB.97.184405
Friedrich, A., Winkler, B., Morgenroth, W., Ruiz-Fuertes, J., Koch-Müller, M., Rhede, D., Milman, V. (2014): Pressure-induced spin collapse of octahedrally coordinated Fe3+ in Ca3Fe2[SiO4]3 from experiment and theory. - Physical Review B, 90, 9, 094105.
https://doi.org/10.1103/PhysRevB.90.094105
Müller, J., Speziale, S., Efthimiopoulos, I., Jahn, S., Koch-Müller, M. (2016): Raman spectroscopy of siderite at high pressure: Evidence for a sharp spin transition. - American Mineralogist, 101, 12, 2638-2644.
https://doi.org/10.2138/am-2016-5708
Contact
Prof. Dr. Monika Koch-Müller
Prof. Dr. Maribel Núñez Valdez
Partners
Dr. Alexandra Friedrich, Institut für Anorganische Chemie, Universität Würzburg
Prof. Michail Taran, Institute of Geochemistry, Mineralogy and Ore Formation, Kyiv
Natural zircon is a host of uranium and thorium and an important tool of geological dating. We examine the phase transitions of natural zircon by means of Raman spectroscopy to obtain a better understanding of the behavior of this mineral in the Earth.
Contact
Dr. Hans Josef Reichmann
Partner
Dr. Alexander Rocholl, GFZ
Tourmaline has been widely used as a petrogenetical indicator. There is, however, no general agreement if and how the compositional variability of tourmaline could be potentially used as a geobarometer. We want to test the hypothesis of enhanced potassium incorporation as well as increased incorporation of tetrahedral B into the tourmaline structure by a series of tourmaline-fluid (Ca,Na,K)-exchange experiments at ultrahigh pressure. If so, significant tetrahedral B must have a significant effect on the B isotope fractionation between fluid and tourmaline, which will be calibrated. The experimental part of the project will be accompanied by crystal-chemical and B isotopic analyses of tourmaline from high- and ultrahigh pressure rocks using well-known, previously characterized samples. We expect a better understanding of the large-scale, long-term B cycle during subduction processes.
Contact
Dr. Bernd Wunder / Prof. Dr. Wilhelm Heinrich
Partners
Dr. Birgit Plessen, GFZ / Dr. Alexander Rocholl, GFZ / Dr. Robert Trumbull, GFZ / Dr. Eleanor Berryman, Department of Geosciences, Princeton University / Dr. Andreas Ertl, Institut für Mineralogie und Kristallographie, Universität Wien / Prof. Dr. Gerhard Franz, Angewandte Geowissenschaften, Technische Universität Berlin / Dr. Piotr Kowalski, Institute of Energy and Climate Research, Forschungszentrum Jülich / Dr. Martin Kutzschbach, Angewandte Geowissenschaften, Technische Universität Berlin
Publications
Kutzschbach, M., Wunder, B., Wannhoff, I., Wilke, F., Couffignal, F., Rocholl, A. (2021): Raman spectroscopic quantification of tetrahedral boron in synthetic aluminum-rich tourmaline. - American Mineralogist, 106, 6, 872-882.
https://doi.org/10.2138/am-2021-7758
Vereshchagin, O. S., Britvin, S. N., Wunder, B., Frank-Kamenetskaya, O. V., Wilke, F., Vlasenko, N. S., Shilovskikh, V. V., Bocharov, V. N., Danilov, D. V. (2021): Ln3+ (Ln3+ = La, Nd, Eu, Yb) incorporation in synthetic tourmaline analogues: Towards tourmaline REE pattern explanation. - Chemical Geology, 584, 120526.
https://doi.org/10.1016/j.chemgeo.2021.120526
Berryman, E. J., Zhang, D., Wunder, B., Duffy, T. S. (2019): Compressibility of synthetic Mg-Al tourmalines to 60 GPa. - American Mineralogist, 104, 7, 1005-1015.
https://doi.org/10.2138/am-2019-6967
Kesterite Cu2ZnSnS4
Chalcogenide semiconductors have attracted significant attention over the last decades, as ideal candidates for photovoltaic applications. Among the various candidates for this purpose, the quaternary Cu2ZnSnS4 compound constitutes a promising material due to:
- a) an almost optimal band gap (Eg ~ 1.5 eV),
- b) its large absorption coefficient in the visible range (~ 104 cm-1),
- c) demonstrated power conversion efficiencies close to 10%,
- d) the high natural abundance and
- e) the non-toxicity of its constituents.
Nevertheless, the power conversion efficiency of Cu2ZnSnS4 thin films still lies far away from the theoretical limit of ~ 30%. Hence, it becomes imperative to explore the physical properties of this system also as a function of pressure further, as a means of improving its photovoltaic performance.
The scientific goal of this project is the investigation of the pressure-induced effects on these materials by means of vibrational spectroscopy (in-house) and x-ray diffraction (synchrotron-based experiments). Our results will enrich current efforts worldwide for finding suitable earth-related substitutes for energy applications.
Mg-Fe-N and Ge-Si solid solutions
Nitrides and Ge-Si solid solutions are important materials in design, power and information engineering as well as in the semiconductor industry. In this project we examine the high pressure and high temperature conditions of the magnesium-iron-nitrides and the Ge-Si synthesis. We employ multi-anvil apparatus and diamond anvil cells in the synchrotron storage rings in Hamburg (PETRA III) and in Grenoble, France (ESRF).
Contact
Dr. Ilias Efthimiopoulos / Dr. Hans Josef Reichmann
Partners
Prof. Dr. Martin Lerch, TU Berlin / Dr. George Serghiou, School of Engineering, The University of Edinburgh, UK
This project focuses on important steps in the resolution of fundamental questions regarding pegmatite-forming media and processes, including:
- water concentration in real pegmatite melts,
- separation from the granitic host, as critical step,
- melt-melt-fluid immiscibility,
- main and trace element distribution in different melt and fluid phases,
- extreme enrichment of water, alkalis and boron and its consequences,
- significance of the high-temperature sol-gel state, especially during the formation of the quartz core.
An important tool in this intricate task are the fluid and melt inclusions in minerals as media for the deciphering mineral-forming processes, constraining the temperature, pressure and the compositions of the long-gone fluids which were actively involved in the different mineral-forming environments during pegmatite formation. Thus, studies of melt and fluid inclusions provide the critical evidence for liquid compositions and phase relations in nature. Our philosophy for further progress in this field is always to combine natural observations, including the inclusion research, with experimental and analytical studies of key subsystems.
Contact
Dr. Rainer Thomas
FOR 2125 - Structures, properties and reactions of carbonates at high pressures and temperatures - CarboPaT
The research unit FOR2125 was funded from 2015 to 2022 by the DFG.
Here are some selected publications from our section:
Martirosyan, N., Efthimiopoulos, I., Jahn, S., Lobanov, S., Wirth, R., Reichmann, H.-J., Koch-Müller, M. (2024): High - pressure polymorphs of the ferroan dolomite: possible host structures for carbon in the lower mantle. - American Mineralogist, 109, 4, 701-708.
https://doi.org/10.2138/am-2022-8737
Pennacchioni, L., Martirosyan, N., Pakhomova, A., König, J., Wirth, R., Jahn, S., Koch-Müller, M., Speziale, S. (2023): Crystal structure and high-pressure phase behavior of a CaCO3–SrCO3 solid solution. - Physics and Chemistry of Minerals, 50, 29.
https://doi.org/10.1007/s00269-023-01252-7
Sieber, M. J., Reichmann, H.-J., Farla, R., Koch-Müller, M. (2023 online): Stability Of Magnesite In The Presence Of Hydrous Fluids Up To 12 Gpa: Insights Into Subduction Zone Processes And Carbon Cycling In The Earth’s Mantle. - American Mineralogist.
https://doi.org/10.2138/am-2023-8982
Pennacchioni, L., Speziale, S., Winkler, B. (2023): Elasticity of natural aragonite samples by Brillouin spectroscopy. - Physics and Chemistry of Minerals, 50, 22.
https://doi.org/10.1007/s00269-023-01244-7
Müller, J., Speziale, S., Efthimiopoulos, I., Jahn, S., Koch-Müller, M. (2016): Raman spectroscopy of siderite at high pressure: Evidence for a sharp spin transition. - American Mineralogist, 101, 12, 2638-2644.
https://doi.org/10.2138/am-2016-5708
Structural properties of carbonate-silicate melts and their effect on fractionation processes in the deep Earth investigated by synchrotron radiation, spectroscopic, and ion probe methods
Pohlenz J., Pascarelli S., O Mathon O., Belin S., A Shiryaev A., Safonov O., Veligzhanin A., Murzin V., Irifune T., Wilke M. (2016) Structural properties of sodium-rich carbonate-silicate melts: An in-situ high-pressure EXAFS study on Y and Sr. Journal of Physics: Conference Series 712, 012083. doi: 10.1088/1742-6596/712/1/012083
Rosa A.D., Pohlenz J., de Grouchy C., Cochain B., Kono Y., Pasternak S., Mathon O., Irifune T., Wilke M. (2016) In situ characterization of liquid network structures at high pressure and temperature using X-ray absorption spectroscopy coupled with the Paris-Edinburgh press. High Pressure Research. doi: 10.1080/08957959.2016.1199693
Pohlenz, J., Rosa, A., Mathon, O., Pascarelli, S., Belin, S., Landrot, G., Murzin, V., Veligzhanin, A., Shiryaev, A., Irifune, T., Wilke, M. (2018) Structural controls of CO2 on Y, La and Sr incorporation in sodium-rich silicate - carbonate melts by in-situ high P-T EXAFS. Chemical Geology. doi: 10.1016/j.chemgeo.2017.12.023
The research unit "Nanoscale processes and geomaterials properties" has been funded from 2007 to 2016 by the German Science Foundation (DFG) and the Austrian Science Fund (FWF).
The research included several closely interconnected projects such as (1) atomic structure, thermodynamic and kinetic properties of grain boundaries, (2) diffusion in polycrystals, (3) exsolution in mineral systems and (4) fluid assisted mineral replacement. Among others, projects addressed how grain- and phase boundaries are generated during homogeneous and heterogeneous nucleation, and how the network of grain and phase boundaries may evolve during thermally and stress induced re-crystallization. The focus lied on experimentation and theoretical work, and was complemented by studies on natural material and applied mineralogy.
The speakers of the Research Group Wilhelm Heinrich (GFZ) and Rainer Abart (University of Vienna) organised an EMU school on Mineral Reaction Kinetics from 19-23 September 2016 in Vienna and are editors of the EMU Notes in Mineralogy, Volume 16 "Mineral reaction kinetics: microstructures, textures, chemical and isotopic signatures".
In many processes in the Earth’s crust and mantle fluids are involved. The formation of melts, the metasomatic alteration of rocks and more or less any material transport but also the rheological properties of minerals and rocks are influenced by the thermodynamic properties of fluids.
Churakov, S. V., Gottschalk, M. (2003): Perturbation theory based equation of state for polar molecular fluids: I. Pure fluids. - Geochimica et Cosmochimica Acta, 67, 13, 2397-2414.
https://doi.org/10.1016/S0016-7037(02)01347-9
Churakov, S. V., Gottschalk, M. (2003): Perturbation theory based equation of state for polar molecular fluids: II. Fluid mixtures. - Geochimica et Cosmochimica Acta, 67, 13, 2415-2425.
https://doi.org/10.1016/S0016-7037(02)01348-0
Contact
Prof. Dr. Matthias Gottschalk