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286 results on '"Langenhorst F"'

1. Novel experimental setup for megahertz X‐ray diffraction in a diamond anvil cell at the High Energy Density (HED) instrument of the European X‐ray Free‐Electron Laser (EuXFEL)

Author

Liermann, HP, Konôpková, Z, Appel, K, Prescher, C, Schropp, A, Cerantola, V, Husband, RJ, McHardy, JD, McMahon, MI, McWilliams, RS, Pépin, CM, Mainberger, J, Roeper, M, Berghäuser, A, Damker, H, Talkovski, P, Foese, M, Kujala, N, Ball, OB, Baron, MA, Briggs, R, Bykov, M, Bykova, E, Chantel, J, Coleman, AL, Cynn, H, Dattelbaum, D, Dresselhaus-Marais, LE, Eggert, JH, Ehm, L, Evans, WJ, Fiquet, G, Frost, M, Glazyrin, K, Goncharov, AF, Hwang, H, Jenei, Zs, Kim, J-Y, Langenhorst, F, Lee, Y, Makita, M, Marquardt, H, McBride, EE, Merkel, S, Morard, G, O'Bannon, EF, Otzen, C, Pace, EJ, Pelka, A, Pigott, JS, Prakapenka, VB, Redmer, R, Sanchez-Valle, C, Schoelmerich, M, Speziale, S, Spiekermann, G, Sturtevant, BT, Toleikis, S, Velisavljevic, N, Wilke, M, Yoo, C-S, Baehtz, C, Zastrau, U, and Strohm, C

Subjects
diamond anvil cells, X-ray free-electron lasers, high-precision X-ray diffraction, finite element modeling, Condensed Matter Physics, Optical Physics, Physical Chemistry (incl. Structural), Biophysics
Abstract

The high-precision X-ray diffraction setup for work with diamond anvil cells (DACs) in interaction chamber 2 (IC2) of the High Energy Density instrument of the European X-ray Free-Electron Laser is described. This includes beamline optics, sample positioning and detector systems located in the multipurpose vacuum chamber. Concepts for pump-probe X-ray diffraction experiments in the DAC are described and their implementation demonstrated during the First User Community Assisted Commissioning experiment. X-ray heating and diffraction of Bi under pressure, obtained using 20 fs X-ray pulses at 17.8 keV and 2.2 MHz repetition, is illustrated through splitting of diffraction peaks, and interpreted employing finite element modeling of the sample chamber in the DAC.

Published
2021

2. A comprehensive study of apatite grains in Ryugu rock fragments

Author

Tkalcec, B. J., primary, Tack, P., additional, De Pauw, E., additional, Bazi, B., additional, Vekemans, B., additional, Lindner, M., additional, Vincze, L., additional, Di Michiel, M., additional, Garrevoet, J., additional, Falkenberg, G., additional, Nakamura, T., additional, Morita, T., additional, Amano, K., additional, Nakashima, D., additional, Langenhorst, F., additional, Pollok, K., additional, Yurimoto, H., additional, Noguchi, T., additional, Okazaki, R., additional, Yabuta, H., additional, Naraoka, H., additional, Sakamoto, K., additional, Tachibana, S., additional, Yada, T., additional, Nishimura, M., additional, Nakato, A., additional, Miyazaki, A., additional, Yogata, K., additional, Abe, M., additional, Okada, T., additional, Usui, T., additional, Yoshikawa, M., additional, Saiki, T., additional, Tanaka, S., additional, Terui, F., additional, Nakazawa, S., additional, Watanabe, S., additional, Tsuda, Y., additional, and Brenker, F. E., additional

Published
2024
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5. SHERLOC investigation for Mars 2020

Author

Beegle, L. W, Bhartia, R, DeFlores, L, Abbey, W, Asher, S, Burton, A, Carrier, B, Conrad, P, Clegg, S, Edgett, K.S, Ehlmann, B, Fries, M, Hug, W, Kah, L, Nealson, K, Nelson, Tony, Minitti, M, Popp, J, Langenhorst, F, Orphan, V, Ravine, M.A, Reid, R, Sobron, P, Steele, A, Tarcea, N, Wanger, G, Wiens, R, Williford, K, and Yingst, R. A

Published
2019

6. SHERLOC investigation for Mars 2020

Author

Yingst, R. A, Williford, K, Wiens, R, Wanger, G, Tarcea, N, Steele, A, Sobron, P, Reid, R, Ravine, M.A, Orphan, V, Langenhorst, F, Popp, J, Minitti, M, Nelson, Tony, Nealson, K, Kah, L, Hug, W, Fries, M, Ehlmann, B, Edgett, K.S, Clegg, S, Conrad, P, Carrier, B, Burton, A, Asher, S, Abbey, W, DeFlores, L, Bhartia, R, and Beegle, L. W

Abstract

UNKNOWN

Published
2019

7. Formation and evolution of carbonaceous asteroid Ryugu: Direct evidence from returned samples

Author

Nakamura, T., primary, Matsumoto, M., additional, Amano, K., additional, Enokido, Y., additional, Zolensky, M. E., additional, Mikouchi, T., additional, Genda, H., additional, Tanaka, S., additional, Zolotov, M. Y., additional, Kurosawa, K., additional, Wakita, S., additional, Hyodo, R., additional, Nagano, H., additional, Nakashima, D., additional, Takahashi, Y., additional, Fujioka, Y., additional, Kikuiri, M., additional, Kagawa, E., additional, Matsuoka, M., additional, Brearley, A. J., additional, Tsuchiyama, A., additional, Uesugi, M., additional, Matsuno, J., additional, Kimura, Y., additional, Sato, M., additional, Milliken, R. E., additional, Tatsumi, E., additional, Sugita, S., additional, Hiroi, T., additional, Kitazato, K., additional, Brownlee, D., additional, Joswiak, D. J., additional, Takahashi, M., additional, Ninomiya, K., additional, Takahashi, T., additional, Osawa, T., additional, Terada, K., additional, Brenker, F. E., additional, Tkalcec, B. J., additional, Vincze, L., additional, Brunetto, R., additional, Aléon-Toppani, A., additional, Chan, Q. H. S., additional, Roskosz, M., additional, Viennet, J.-C., additional, Beck, P., additional, Alp, E. E., additional, Michikami, T., additional, Nagaashi, Y., additional, Tsuji, T., additional, Ino, Y., additional, Martinez, J., additional, Han, J., additional, Dolocan, A., additional, Bodnar, R. J., additional, Tanaka, M., additional, Yoshida, H., additional, Sugiyama, K., additional, King, A. J., additional, Fukushi, K., additional, Suga, H., additional, Yamashita, S., additional, Kawai, T., additional, Inoue, K., additional, Nakato, A., additional, Noguchi, T., additional, Vilas, F., additional, Hendrix, A. R., additional, Jaramillo-Correa, C., additional, Domingue, D. L., additional, Dominguez, G., additional, Gainsforth, Z., additional, Engrand, C., additional, Duprat, J., additional, Russell, S. S., additional, Bonato, E., additional, Ma, C., additional, Kawamoto, T., additional, Wada, T., additional, Watanabe, S., additional, Endo, R., additional, Enju, S., additional, Riu, L., additional, Rubino, S., additional, Tack, P., additional, Takeshita, S., additional, Takeichi, Y., additional, Takeuchi, A., additional, Takigawa, A., additional, Takir, D., additional, Tanigaki, T., additional, Taniguchi, A., additional, Tsukamoto, K., additional, Yagi, T., additional, Yamada, S., additional, Yamamoto, K., additional, Yamashita, Y., additional, Yasutake, M., additional, Uesugi, K., additional, Umegaki, I., additional, Chiu, I., additional, Ishizaki, T., additional, Okumura, S., additional, Palomba, E., additional, Pilorget, C., additional, Potin, S. M., additional, Alasli, A., additional, Anada, S., additional, Araki, Y., additional, Sakatani, N., additional, Schultz, C., additional, Sekizawa, O., additional, Sitzman, S. D., additional, Sugiura, K., additional, Sun, M., additional, Dartois, E., additional, De Pauw, E., additional, Dionnet, Z., additional, Djouadi, Z., additional, Falkenberg, G., additional, Fujita, R., additional, Fukuma, T., additional, Gearba, I. R., additional, Hagiya, K., additional, Hu, M. Y., additional, Kato, T., additional, Kawamura, T., additional, Kimura, M., additional, Kubo, M. K., additional, Langenhorst, F., additional, Lantz, C., additional, Lavina, B., additional, Lindner, M., additional, Zhao, J., additional, Vekemans, B., additional, Baklouti, D., additional, Bazi, B., additional, Borondics, F., additional, Nagasawa, S., additional, Nishiyama, G., additional, Nitta, K., additional, Mathurin, J., additional, Matsumoto, T., additional, Mitsukawa, I., additional, Miura, H., additional, Miyake, A., additional, Miyake, Y., additional, Yurimoto, H., additional, Okazaki, R., additional, Yabuta, H., additional, Naraoka, H., additional, Sakamoto, K., additional, Tachibana, S., additional, Connolly, H. C., additional, Lauretta, D. S., additional, Yoshitake, M., additional, Yoshikawa, M., additional, Yoshikawa, K., additional, Yoshihara, K., additional, Yokota, Y., additional, Yogata, K., additional, Yano, H., additional, Yamamoto, Y., additional, Yamamoto, D., additional, Yamada, M., additional, Yamada, T., additional, Yada, T., additional, Wada, K., additional, Usui, T., additional, Tsukizaki, R., additional, Terui, F., additional, Takeuchi, H., additional, Takei, Y., additional, Iwamae, A., additional, Soejima, H., additional, Shirai, K., additional, Shimaki, Y., additional, Senshu, H., additional, Sawada, H., additional, Saiki, T., additional, Ozaki, M., additional, Ono, G., additional, Okada, T., additional, Ogawa, N., additional, Ogawa, K., additional, Noguchi, R., additional, Noda, H., additional, Nishimura, M., additional, Namiki, N., additional, Nakazawa, S., additional, Morota, T., additional, Miyazaki, A., additional, Miura, A., additional, Mimasu, Y., additional, Matsumoto, K., additional, Kumagai, K., additional, Kouyama, T., additional, Kikuchi, S., additional, Kawahara, K., additional, Kameda, S., additional, Iwata, T., additional, Ishihara, Y., additional, Ishiguro, M., additional, Ikeda, H., additional, Hosoda, S., additional, Honda, R., additional, Honda, C., additional, Hitomi, Y., additional, Hirata, N., additional, Hayashi, T., additional, Hayakawa, M., additional, Hatakeda, K., additional, Furuya, S., additional, Fukai, R., additional, Fujii, A., additional, Cho, Y., additional, Arakawa, M., additional, Abe, M., additional, and Tsuda, Y., additional

Published
2023
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9. Mineral Matter in Space

Author

Marfunin, A. S., Wynn-Williams, C. G., Fisenko, A. V., Rietmeijer, F. J. M., Kurat, G., Kozenko, A. V., Zharkov, V. N., Kuskov, O. L., Ulyanov, A. A., Kashkarov, L. L., Deutsch, A., Langenhorst, F., Masaitis, V. L., Nazarov, M. A., and Marfunin, Arnold S., editor

Published
1998
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15. Reaction‐Induced Mantle Weakening at High‐Pressure Conditions: An Example From Garnet Pyroxenites of Ulten Zone (Eastern Alps, N Italy)

Author

Pellegrino, L, Menegon, L, Zanchetta, S, Langenhorst, F, Pollok, K, Tumiati, S, Malaspina, N, Pellegrino, L, Menegon, L, Zanchetta, S, Langenhorst, F, Pollok, K, Tumiati, S, and Malaspina, N

Abstract

Peridotites of Ulten Zone (Eastern Alps, N Italy) show a transition from coarse protogranular spinel lherzolites to fine-grained amphibole + garnet peridotites, recorded by the crystallization of garnet coronas around spinel. Pyroxenite veins, transposed along the peridotite foliation, show a similar metamorphic evolution from coarse-grained (garnet-free) websterites to fine-grained garnet websterites. In both peridotites and websterites, garnet previously exsolved from porphyroclastic high-temperature pyroxenes and later crystallized along the foliation. This evolution has been interpreted to reflect cooling and pressure increase of websterites and host peridotites from spinel- to garnet-facies conditions. Microstructures and crystallographic orientation data indicate that the re-equilibration of garnet websterites in the garnet stability field occurred during deformation. Porphyroclastic pyroxenes have been interpreted to deform by dislocation glide and creep. In particular, TEM observations indicate the activation of the (100)[010] slip system in orthopyroxene. Core-and-mantle microstructures also suggest that dislocation creep was aided by subgrain rotation recrystallization, leading to the formation of neoblastic pyroxenes. These recrystallized grains deformed by diffusion-accommodated grain boundary sliding, as indicated by the occurrence of quadruple junctions and straight, aligned grain boundaries. The transition from dislocation creep to diffusion creep in websterites was accompanied by the crystallization of garnet along foliation, which triggered the pinning of the recrystallized matrix and stabilized the fine-grained microtexture for diffusion creep, promoting rheological weakening. Garnet websterites of Ulten Zone thus offer a unique opportunity to investigate the effects of reaction softening during the corner flow in the supra-subduction lithospheric mantle induced by the descending slab.

Published
2021

16. Novel experimental setup for megahertz X-ray diffraction in a diamond anvil cell at the High Energy Density (HED) instrument of the European X-ray Free-Electron Laser (EuXFEL)

Author

Liermann, H. P., Konôpková, Z., Appel, K., Prescher, C., Schropp, A., Cerantola, V., Husband, R. J., McHardy, J. D., McMahon, M. I., McWilliams, R. S., Pépin, C. M., Mainberger, J., Roeper, M., Berghäuser, A., Damker, H., Talkovski, P., Foese, M., Kujala, N., Ball, O. B., Baron, M. A., Briggs, R., Bykov, M., Bykova, E., Chantel, J., Coleman, A. L., Cynn, H., Dattelbaum, D., Dresselhaus-Marais, L. E., Eggert, J. H., Ehm, L., Evans, W. J., Fiquet, G., Frost, M., Glazyrin, K., Goncharov, A. F., Hwang, H., Jenei, Z., Kim, J.-Y., Langenhorst, F., Lee, Y., Makita, M., Marquardt, H., McBride, E. E., Merkel, S., Morard, G., Obannon, E. F., Otzen, C., Pace, E. J., Pelka, A., Pigott, J. S., Prakapenka, V. B., Redmer, R., Sanchez-Valle, C., Schölmerich, M., Speziale, S., Spiekermann, G., Sturtevant, B. T., Toleikis, S., Velisavljevic, N., Wilke, M., Yoo, C.-S., Baehtz, C., Zastrau, U., Strohm, C., Liermann, H. P., Konôpková, Z., Appel, K., Prescher, C., Schropp, A., Cerantola, V., Husband, R. J., McHardy, J. D., McMahon, M. I., McWilliams, R. S., Pépin, C. M., Mainberger, J., Roeper, M., Berghäuser, A., Damker, H., Talkovski, P., Foese, M., Kujala, N., Ball, O. B., Baron, M. A., Briggs, R., Bykov, M., Bykova, E., Chantel, J., Coleman, A. L., Cynn, H., Dattelbaum, D., Dresselhaus-Marais, L. E., Eggert, J. H., Ehm, L., Evans, W. J., Fiquet, G., Frost, M., Glazyrin, K., Goncharov, A. F., Hwang, H., Jenei, Z., Kim, J.-Y., Langenhorst, F., Lee, Y., Makita, M., Marquardt, H., McBride, E. E., Merkel, S., Morard, G., Obannon, E. F., Otzen, C., Pace, E. J., Pelka, A., Pigott, J. S., Prakapenka, V. B., Redmer, R., Sanchez-Valle, C., Schölmerich, M., Speziale, S., Spiekermann, G., Sturtevant, B. T., Toleikis, S., Velisavljevic, N., Wilke, M., Yoo, C.-S., Baehtz, C., Zastrau, U., and Strohm, C.

Abstract

The high-precision X-ray diffraction setup for work with diamond anvil cells (DACs) in interaction chamber 2 (IC2) of the High Energy Density instrument of the European X-ray Free-Electron Laser is described. This includes beamline optics, sample positioning and detector systems located in the multipurpose vacuum chamber. Concepts for pump–probe X-ray diffraction experiments in the DAC are described and their implementation demonstrated during the First User Community Assisted Commissioning experiment. X-ray heating and diffraction of Bi under pressure, obtained using 20 fs X-ray pulses at 17.8 keV and 2.2 MHz repetition, is illustrated through splitting of diffraction peaks, and interpreted employing finite element modeling of the sample chamber in the DAC.

Published
2021

17. Novel experimental setup for megahertz X-ray diffraction in a diamond anvil cell at the High Energy Density (HED) instrument of the European X-ray Free-Electron Laser (EuXFEL)

Author

Liermann, H, Konôpková, Z, Appel, K, Prescher, C, Schropp, A, Cerantola, V, Husband, R, Mchardy, J, Mcmahon, M, Mcwilliams, R, Pépin, C, Mainberger, J, Roeper, M, Berghäuser, A, Damker, H, Talkovski, P, Foese, M, Kujala, N, Ball, O, Baron, M, Briggs, R, Bykov, M, Bykova, E, Chantel, J, Coleman, A, Cynn, H, Dattelbaum, D, Dresselhaus-Marais, L, Eggert, J, Ehm, L, Evans, W, Fiquet, G, Frost, M, Glazyrin, K, Goncharov, A, Hwang, H, Jenei, Z, Kim, J, Langenhorst, F, Lee, Y, Makita, M, Marquardt, H, Mcbride, E, Merkel, S, Morard, G, O'Bannon, E, Otzen, C, Pace, E, Pelka, A, Pigott, J, Prakapenka, V, Redmer, R, Sanchez-Valle, C, Schoelmerich, M, Speziale, S, Spiekermann, G, Sturtevant, B, Toleikis, S, Velisavljevic, N, Wilke, M, Yoo, C, Baehtz, C, Zastrau, U, Strohm, C, Liermann, H P, Husband, R J, McHardy, J D, McMahon, M I, McWilliams, R S, Pépin, C M, Ball, O B, Baron, M A, Coleman, A L, Dresselhaus-Marais, L E, Eggert, J H, Evans, W J, Goncharov, A F, Jenei, Zs, Kim, J Y, McBride, E E, O'Bannon, E F, Pace, E J, Pigott, J S, Prakapenka, V B, Sturtevant, B T, Yoo, C S, Liermann, H, Konôpková, Z, Appel, K, Prescher, C, Schropp, A, Cerantola, V, Husband, R, Mchardy, J, Mcmahon, M, Mcwilliams, R, Pépin, C, Mainberger, J, Roeper, M, Berghäuser, A, Damker, H, Talkovski, P, Foese, M, Kujala, N, Ball, O, Baron, M, Briggs, R, Bykov, M, Bykova, E, Chantel, J, Coleman, A, Cynn, H, Dattelbaum, D, Dresselhaus-Marais, L, Eggert, J, Ehm, L, Evans, W, Fiquet, G, Frost, M, Glazyrin, K, Goncharov, A, Hwang, H, Jenei, Z, Kim, J, Langenhorst, F, Lee, Y, Makita, M, Marquardt, H, Mcbride, E, Merkel, S, Morard, G, O'Bannon, E, Otzen, C, Pace, E, Pelka, A, Pigott, J, Prakapenka, V, Redmer, R, Sanchez-Valle, C, Schoelmerich, M, Speziale, S, Spiekermann, G, Sturtevant, B, Toleikis, S, Velisavljevic, N, Wilke, M, Yoo, C, Baehtz, C, Zastrau, U, Strohm, C, Liermann, H P, Husband, R J, McHardy, J D, McMahon, M I, McWilliams, R S, Pépin, C M, Ball, O B, Baron, M A, Coleman, A L, Dresselhaus-Marais, L E, Eggert, J H, Evans, W J, Goncharov, A F, Jenei, Zs, Kim, J Y, McBride, E E, O'Bannon, E F, Pace, E J, Pigott, J S, Prakapenka, V B, Sturtevant, B T, and Yoo, C S

Abstract

The high-precision X-ray diffraction setup for work with diamond anvil cells (DACs) in interaction chamber 2 (IC2) of the High Energy Density instrument of the European X-ray Free-Electron Laser is described. This includes beamline optics, sample positioning and detector systems located in the multipurpose vacuum chamber. Concepts for pump-probe X-ray diffraction experiments in the DAC are described and their implementation demonstrated during the First User Community Assisted Commissioning experiment. X-ray heating and diffraction of Bi under pressure, obtained using 20 fs X-ray pulses at 17.8 keV and 2.2 MHz repetition, is illustrated through splitting of diffraction peaks, and interpreted employing finite element modeling of the sample chamber in the DAC.

Published
2021

18. Reaction-induced rheological weakening in the supra-subduction mantle: an example from garnet pyroxenites of Ulten zone (Eastern Alps, N Italy)

Author

Pellegrino, L, Menegon, L, Zanchetta, S, Langenhorst, F, Pollok, K, Tumiati, S, Malaspina N, Malaspina, N, Pellegrino, Luca, Menegon, Luca, Zanchetta, Stefano, Langenhorst, Falko, Pollok, Kilian, Tumiati, Simone, Malaspina, Nadia, Pellegrino, L, Menegon, L, Zanchetta, S, Langenhorst, F, Pollok, K, Tumiati, S, Malaspina N, Malaspina, N, Pellegrino, Luca, Menegon, Luca, Zanchetta, Stefano, Langenhorst, Falko, Pollok, Kilian, Tumiati, Simone, and Malaspina, Nadia

Abstract

Pyroxenites are common compositional heterogeneities in the upper mantle and represent key lithologies in mantle deformation processes, as the local presence of pyroxene-rich compositions can weaken the mantle strength. Pyroxenites occur ubiquitously as variably deformed layers in most of oceanic and orogenic peridotite massifs, and thus can be used as a proxy to investigate the rheological behavior of the mantle in different geodynamic settings, including subduction zones. In the Ulten Zone (Tonale nappe, Eastern Alps, N Italy), numerous peridotite bodies occur within high-grade crustal rocks. Peridotites show a transition from coarse protogranular spinel lherzolites to finer-grained amphibole + garnet peridotites (Obata and Morten, 1987). Pyroxenites veins and dikes, transposed along the peridotite foliation, show a similar evolution from coarse garnet-free websterites to finer-grained garnet clinopyroxenites (Morten and Obata, 1983). This evolution has been interpreted to reflect cooling and pressure increase of pyroxenites and host peridotites from spinel- (1200 °C, 1.3-1.6 GPa) to garnet-facies conditions (850 °C and 2.7 GPa) within the mantle corner flow (Nimis and Morten, 2000). This results in the consequent formation of garnet at the expense of spinel. In particular, garnet initially formed as coronas around spinel and as exsolution lamellae in high-T pyroxenes, and later as neoblasts along the foliation of pyroxenites and host peridotites. Microstructures and crystallographic orientation data indicate that the transition from spinel- to garnet-facies conditions occurred in a deformation regime. Pyroxene porphyroclasts in garnet clinopyroxenites show well-developed crystallographic preferred orientation, high frequency of low-angle misorientations, and non-random distribution of the low-angle misorientation axes. These features indicate that pyroxene porphyroclasts primarily deformed by grain size insensitive (GSI) creep. Core-and-mantle microstructures in

Published
2021

19. Order and miscibility in the otavite--magnesite solid solution

Author

Bromiley, F.A., Ballaran, T. Boffa, Langenhorst, F., and Seifert, F.

Subjects
Solid solutions -- Chemical properties, Phase transformations (Statistical physics) -- Observations, Carbonate minerals -- Chemical properties, Solubility -- Analysis, Earth sciences
Abstract

The effects of cation substitution and ordering in the otavite (CdC[O.sub.3])-magnesite (MgC[O.sub.3]) solid solution have been investigated on samples synthesized at 1 GPa in the temperature range 500-800 [degrees]C for run durations up to 120 h. A complete, disordered solid solution, with R3c symmetry, was obtained at 800 [degrees]C, whereas Mg and Cd show partial ordering within the cadmium dolomite stability field, with R[bar.3] symmetry, at intermediate compositions in the temperature range 500-650 [degrees]C. Rietveld refinements for X-ray diffraction data show that variation of the a-axis is linear as a function of composition, independent of the degree of order, whereas the c-axis shows a positive deviation from linearity as a function of composition, decreasing with increasing degree of order. Octahedral bond distances of the 800 [degrees]C series vary linearly with composition. Site occupancies were used to determine the long-range order parameter, Q, for samples with R[bar.3] symmetry. [Q.sup.4] vades linearly as a function of temperature, suggesting a tricritical phase transition with a critical transition temperature [T.sub.c] of 702(10) [degrees]C. EDXTEM compositional microanalyses of samples within two-phase regions are in good agreement with Rietveld refinements, and allow better constraint of phase boundaries. Keywords: X-ray powder diffraction, otavite--magnesite solid solution, carbonates, phase transition, cation ordering

Published
2007

20. The effect of valence state and site geometry on Ti [L.sub.3,2] and O K electron energy-loss spectra of [Ti.sub.x][O.sub.y] phases

Author

Stoyanov, E., Langenhorst, F., and Steinle-Neumann, G.

Subjects
Density functionals -- Analysis, Transmission electron microscopes -- Research, Earth sciences
Abstract

Titanium [L.sub.3,2] and O K electron energy loss near-edge structures (ELNES) of seven Ti oxides have been measured in a transmission electron microscope to obtain information on the valence state and site geometry of Ti. The coordination of Ti in all phases studied is octahedral, whereas the valence states occurring are [Ti.sup.2+], [Ti.sup.3+], and [Ti.sup.4+]. Effects of polyhedra distortions are particularly observed for two oxides with mixed [Ti.sup.3+]-[Ti.sup.4+] valence state, i.e., the Magneli phases [Ti.sub.4][O.sub.7] and [Ti.sub.5][O.sub.9]. A prominent pre-peak in the Ti [L.sub.3] edge is attributed to the orthorhombic polyhedra distortions in these compounds, leading to complex crystal field splitting. The effect of valence state manifests itself in a systematic chemical shift of Ti white lines by 2 eV per valence state. On the basis of collected Ti [L.sub.3,2] ELNES spectra we propose a new quantification technique for the determination of [Ti.sup.4+]/[Ti.sup.3+] ratios. Complementary O K ELNES spectra were well reproduced by Density Functional Theory calculation, revealing that the O K-edge is sensitive to the covalent bonding in all analyzed oxides. Keywords: Electron energy loss spectroscopy, valence state of titanium, titanium oxides, density functional theory

Published
2007

24. Iron-silica interaction at extreme conditions and the electrically conducting layer at the base of Earth's mantle

Author

Dubrovinsky, L., Dubrovinskaia, N., Langenhorst, F., Dobson, D., Rubie, D., Geßmann, C., Abrikosov, I. A., Johansson, B., Baykov, V. I., Vitos, L., Bihan, T. Le, Crichton, W. A., Dmitriev, V., and Weber, H.-P.

Subjects
Environmental issues, Science and technology, Zoology and wildlife conservation
Abstract

Author(s): L. Dubrovinsky (corresponding author) [1]; N. Dubrovinskaia [1]; F. Langenhorst [1]; D. Dobson [1]; D. Rubie [1]; C. Geßmann [2]; I. A. Abrikosov [3]; B. Johansson [3, 4]; V. [...]

Published
2003
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29. Mossbauer and ELNES spectroscopy of (Mg, Fe)(Si, Al)[O.sub.3] perovskite: a highly oxidised component of the lower mantle

Author

Lauterbach, S., McCammon, C.A., van Aken, P., Langenhorst, F., and Seifert F.

Subjects
Mineralogical research -- Reports, Petrology -- Research, Mossbauer effect -- Usage, Spectrum analysis -- Usage, Perovskite -- Research, Earth sciences
Abstract

(Mg, Fe)(Si, Al)[O.sub.3] perovskite samples with varying Fe and Al concentration were synthesised at high pressure and temperature at varying conditions of oxygen fugacity using a multianvil press, and were characterised using ex situ X-ray diffraction, electron microprobe, Mossbauer spectroscopy and analytical transmission electron microscopy. The [Fe.sup.3+]/[SIGMA]Fe ratio was determined from Mossbauer spectra recorded at 293 and 80 K, and shows a nearly linear dependence of [Fe.sup.3+]/ [SIGMA]Fe with Al composition of (Mg, Fe)(Si, Al)[O.sup.3] perovskite. The [Fe.sup.3+]/[SIGMA]Fe values were obtained for selected samples of (Mg, Fe)(Si, Al)[O.sup.3] perovskite using electron energy, loss near-edge structure (ELNES) spectroscopy, and are in excellent agreement with Mossbauer data, demonstrating that [Fe.sup.3+]/[SIGMA]Fe can be determined with a spatial resolution on the order of nm. Oxygen concentrations were determined by combining bulk chemical data with [Fe.sup.3+]/[SIGMA]Fe data determined by Mossbauer spectroscopy, and show a significant concentration of oxygen vacancies in (Mg, Fe)(Si, Al)[O.sup.3] perovskite.

Published
2000

30. The Rochechouart 2017-Cores Rescaled: Major Features

Author

Lambert, P., Alwmark, C., Baratoux, D., Bouley, S., Brack, A., Bruneton, P., Buchner, E., Dence, M. R., Courtin Nomade, A., Duhamel Achin, I., Floch, J. P., French, B. M., Fudge, C., Gattacceca, J., Gibson, R. L., Goderis, S., Grieve, R. A. F., Hauser, N., Hodges, K. V., Hörz, F., Humayun, M., Jourdan, F., Kelley, S. P., Kenkmann, T., Kring, D. A., Langenhorst, F., Lebreton, J. P., Lee, M. R., Lindgren, P., Lofi, J., Lorand, J. P., Luais, B., Masaitis, V., Meunier, A., Moore, C. B., Ormö, J., Osinski, G. R., Petit, S., Pezard, P. R., Pölchau, M., Pohl, J., Quesnel, Y., Jamboz, C., Reeves, H., Reimold, U. W., Rochette, P., Sapers, H. M., Schmieder, M., Schultz, P. H., Susanne Petra Schwenzer, Sharp, T., Schoemaker, C. S., Simpson, S. L., Stöffler, D., Sturkell, E., Trumel, H., Walton, E., Westall, F., Wittmann, A., Wünnemann, K., Ecosystèmes aquatiques et changements globaux (UR EABX), Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA), Centre International de Recherches et de Restitution sur les Impacts et sur Rochechouart (CIRIR), Department of Geology [Lund], Lund University [Lund], Géosciences Environnement Toulouse (GET), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Géosciences Paris Sud (GEOPS), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Centre de biophysique moléculaire (CBM), Université d'Orléans (UO)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Département Géosciences (AREVA-BU Mines), Groupe AREVA, Analytical, Environmental and Geo- Chemistry, Vrije Universiteit Brussel (VUB), Geological Survey of Canada [Ottawa] (GSC Central & Northern Canada), Geological Survey of Canada - Office (GSC), Natural Resources Canada (NRCan)-Natural Resources Canada (NRCan), Université de Limoges (UNILIM), Bureau de Recherches Géologiques et Minières (BRGM) (BRGM), Smithsonian Institution, Arizona State University [Tempe] (ASU), Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), University of the Witwatersrand [Johannesburg] (WITS), University of Western Ontario (UWO), University of Brasilia [Brazil] (UnB), NASA Johnson Space Center (JSC), NASA, Florida State University [Tallahassee] (FSU), School of Earth and Planetary Sciences [Perth], Curtin University [Perth], Planning and Transport Research Centre (PATREC)-Planning and Transport Research Centre (PATREC), The Open University [Milton Keynes] (OU), Department of Geosciences - Earth Sciences [Fribourg], University of Fribourg, Lunar and Planetary Institute [Houston] (LPI), Friedrich-Schiller-Universität = Friedrich Schiller University Jena [Jena, Germany], Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), School of Geographical and Earth Sciences [Univ Glasgow], University of Glasgow, Géosciences Montpellier, Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Université des Antilles (UA), Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Centre de Recherches Pétrographiques et Géochimiques (CRPG), Institut national des sciences de l'Univers (INSU - CNRS)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), A. P. Karpinsky Russian Geological Research Institute (VSEGEI), Institut de Chimie des Milieux et Matériaux de Poitiers (IC2MP), Université de Poitiers-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Center for Meteorite Studies [Tempe], Centro de Astrobiologia [Madrid] (CAB), Instituto Nacional de Técnica Aeroespacial (INTA)-Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Ludwig-Maximilians-Universität München (LMU), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Institut des Sciences de la Terre d'Orléans - UMR7327 (ISTO), Bureau de Recherches Géologiques et Minières (BRGM) (BRGM)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Métallogénie - UMR7327, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Bureau de Recherches Géologiques et Minières (BRGM) (BRGM)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Laboratoire Pierre Süe (LPS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Division of Geological and Planetary Sciences [Pasadena], California Institute of Technology (CALTECH), Brown University, Arizona Geological Survey, CSIRO Land and Water, Commonwealth Scientific and Industrial Research Organisation [Canberra] (CSIRO), Museum für Naturkunde [Berlin], Department of Earth Sciences [Gothenburg], University of Gothenburg (GU), CEA Le Ripault (CEA Le Ripault), Direction des Applications Militaires (DAM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), University of Alberta, LUAIS, Béatrice, Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Université d'Orléans (UO)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS), Vrije Universiteit [Brussels] (VUB), Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Collège de France (CdF)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Institut National de la Recherche Agronomique (INRA), School of Geosciences, University of the Witwatersrand, Johannesburg, South Africa, Friedrich Schiller University Jena [Jena, Germany], Laboratoire de physique et chimie de l'environnement et de l'Espace (LPC2E), UMR 7328 CNRS/Université d'Orléans, Université d'Orléans (UO), School of Geographical and Earth Sciences [Glasgow], Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Université des Antilles (UA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Planétologie et Géodynamique UMR6112 (LPG), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Nantes - Faculté des Sciences et des Techniques, Université de Nantes (UN)-Université de Nantes (UN)-Université d'Angers (UA), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Université de Poitiers-Centre National de la Recherche Scientifique (CNRS), Instituto Nacional de Técnica Aeroespacial (INTA)-Consejo Superior de Investigaciones Científicas [Spain] (CSIC), PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Bureau de Recherches Géologiques et Minières (BRGM) (BRGM)-Observatoire des Sciences de l'Univers en région Centre (OSUC), CEA-CNRS UMR 9956, CEA Saclay, Commissariat à l'énergie atomique et aux énergies alternatives (CEA), CIRIR, Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD), Université d'Orléans (UO)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Collège de France (CdF (institution))-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut National de la Recherche Agronomique (INRA), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), and Université de Fribourg = University of Fribourg (UNIFR)

Subjects
[SDU] Sciences of the Universe [physics], [SDU.STU.PL]Sciences of the Universe [physics]/Earth Sciences/Planetology, [SDU]Sciences of the Universe [physics], [SDU.STU] Sciences of the Universe [physics]/Earth Sciences, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, [SDU.STU.PL] Sciences of the Universe [physics]/Earth Sciences/Planetology, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2019

32. Diamonds from the iridium-rich K-T boundary layer at Arroyo el Mimbral, Tamaulipas, Mexico

Author

Hough, R.M., Gilmour, I., Pillinger, C.T., Langenhorst, F., and Montanari, A.

Subjects
Tamaulipas, Mexico -- Natural resources, Diamonds -- Research, Geology, Stratigraphic -- Cretaceous, Earth sciences
Abstract

Diamonds, up to 30 [[micro]meter] in size, were found in the iridium-rich layer from the K-T boundary site at Arroyo El Mimbral and the spherule bed from Arroyo El Penon, northeastern Mexico. Stepped heating experiments indicate two or more isotopically distinct diamond components with carbon isotopic compositions characteristic of a mixture of carbon sources. The diamonds' crystal form is cubic - not the hexagonal polymorph of diamond, lonsdaleite, which has been used previously to infer formation due to shock transformation of graphite. The size, crystallography, and mineralogic associations of K-T diamonds are similar to those of impact-produced diamonds from the Ries crater in Germany where both shock transformation of graphite and a mode of formation by condensation from a vapor plume have been inferred. The discovery of impact-produced diamonds in association with high Ir contents for these sediments supports their impact origin, K-T age, and the inference that their source was from the buried impact crater of Chicxulub on the Yucatan peninsula, Mexico.

Published
1997

37. Anhydrite EOS and Phase Diagram in Relation to Shock Decomposition

Author

Ivanov, B. A, Langenhorst, F, Deutsch, A, and Hornemann, U

Subjects
Chemistry And Materials (General)
Abstract

In the context of the Chicxulub impact, it became recently obvious that experimental and theoretical research on the shock behavior of sulfates is essential for an assessment of the role of shock-released gases in the K/T mass extinction. The Chicxulub crater is the most important large impact structure where the bolide penetrated a sedimentary layer with large amounts of interbedded anhydrite (Haughton has also significant anhydrite in the target). The sulfuric gas production by shock compression/decompression of anhydrite is an important issue, even if the size of Chicxulub crater is only half of the so far assumed size. The comparison of experimental data for anhydrite, shocked with different techniques at various laboratories, reveals large differences in the threshold pressures for melting and decomposition. To gain insight into this issue, we have made a theoretical investigation of the thermodynamic properties of anhydrite. The project includes the review of data published in the last 40 years - reasons to study anhydrite cover a wide field of interests: from industrial problems of cement and ceramic production to the analysis of nuclear underground explosions in salt domes, conducted in the USA and USSR in the 1970th.

Published
2004

38. Diaplectic Glass Content in Experimentally Shock-loaded Quartz Determined by X-Ray Powder Diffraction

Author

Skala, R, Hoerz, F, and Langenhorst, F

Subjects
Nonmetallic Materials
Abstract

Quartz is the most common mineral of terrestrial crustal rocks and thus a widespread indicator for impact cratering and associated shock metamorphism. Planar deformation features (PDFs) are among the most prominent and diagnostic shock features in quartz and they represent thin lamellae of glass that formed via solid-state transformations. This socalled 'diaplectic' glass becomes pervasive at higher pressures and results in optically isotropic and X-ray-amorphous phases that resemble texturally the original quartz grains (without evidence of melt flow). In the past, it has been shown that the amount of this amorphous material in experimentally shock-loaded quartz correlates with peak shock pressure. Both reports derive the glass content from density measurements of individual crystals employing the equation X(%) = (rho(sub x) - rho(sub 0))/(rho(sub x) - rho(sub gl)), where x and 0 stands for X-ray and average (optical) density, respectively. The density of glass, rho(sub gl), was adopted as 2.2 g/cu cm. Though the same procedures had been applied, the resulting glass content differs significantly among the above studies. In the present study, we are using a new approach based solely on the integral intensity of a single, carefully selected reflection in the XRD pattern, and we will compare our data to those reported in the literature.

Published
2003

39. ROCHECHOUART 2017-DRILLING CAMPAIGN: FIRST RESULTS

Author

Lambert, P., Alwmark, C., Baratoux, D., Bouley, S., Brack, A., Bruneton, P., Buchner, E., Claeys, P., Dence, M.R., Courtin Nomade, A., Duhamel Achin, I., Floch, J.P., French, B.M., Fudge, C., Gattacceca, J., Gibson, R.L., Goderis, S., Grieve, R.A.F., Hodges, K.V., Hörz, F., Humayun, M., Jourdan, F., Kelley, S.P., Kenkmann, T., Kring, D.A., Langenhorst, F., Lee, M.R., Lindgren, P., Lofi, J., Lorand, J.P., Luais, B., Masaitis, V., Meunier, A., Moore, C.B., Ormö, J., Osinski, G.R., Petit, S., Pezard, P.A., Poelchau, M., Pohl, J., Quesnel, Y., Ramboz, C., Reeves, H., Rochette, P., Sapers, H.M., Schmieder, M., Schultz, P.H., Schwenzer, S.P., Sharp, T., Shoemaker, C.S., Simpson, S.L., Stöffler, D., Sturkell, E., Trumel, H., Walton, E., Westall, F., Wittmann, A., Wünnemann, K., Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), and Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)

Subjects
[SDU.STU.PL]Sciences of the Universe [physics]/Earth Sciences/Planetology
Abstract

International audience; Characteristics and initial description of the 18 holes and 515m of cores recovered (cumulative length) at Rochechouart.

Published
2018

42. Ideal and real structures of different forms of carbon, with some remarks on their geological significance

Author

Langenhorst, F, Campione, M, Langenhorst, F, and Campione, M

Abstract

Carbon is found in nature in a huge variety of allotropic forms and recent research in materials science has encouraged the development of technological materials based on nanocarbon. Carbon atoms with sp2 or sp3 hybridization can be thought of as building blocks. Following a bottom-up approach, we show how graphene and diamond molecules are built up and how their properties vary with size, reaching an upper limit with bulk graphite and diamond. Carbon atoms with sp2 hybridization give rise to an impressive number of different materials, such as carbon nanotubes, graphene nanoribbons, porous carbon and fullerene. As in any crystalline phase, the crystal structures of natural carbon allotropes (i.e. graphite and diamond) contain various types of imperfections. These so-called lattice defects are classified by their dimensions into 0D (point), 1D (line), 2D (planar) and 3D (volume) defects. Lattice defects control the physical properties of crystals and are often a fingerprint of the geological environment in which they formed and were modified. Direct observations of lattice defects are commonly accomplished by transmission electron microscopy. We present and discuss the ideal and real structures of carbon allotropes, the energetics of lattice defects and their significance in understanding geological processes and conditions.

Published
2019

43. Laser simulated hypervelocity micrometeoroid impacts: Orientation dependent shock effects in enstatite single crystals

Author

Schmidt, D., Matthäus, G., Nolte, S., Pollok, K., Langenhorst, F., and Publica

Abstract

Introduction: Space weathering, occurring on airless bodies in the solar system, alters the surfaces of planetary materials by micrometeoroid bombardment and solar wind irradiation. The effects of space weathering are responsible for the differences in reflectance spectra between pristine and weathered planetary materials such as darkening and reddening [1]. Pulsed laser experiments are known to reproduce space weathering effects on olivine like melting, the formation of iron nanoparticles and deformation features like dislocations [2] as well as schock effects in general [3]. Comparable observations are made on natural olivines like in lunar or asteroidal samples [4,5]. We performed laser experiments on pyroxene, which is besides olivine one of the most important planetary minerals. Material and Methods: Kilosa enstatite containing about 4 wt% Fe (En93) was cut perpendicular to the crystallographic axes, i.e. parallel to the (100), (010) and (001) planes. Additionally samples were prepared with parallel to the (210), (211) and (301) planes. The femtosecond laser experiments were conducted at the Institute of Applied Physics at FSU Jena. Laser irradiation was performed on the polished surfaces under vacuum (10-3 mbar) using a Ti:sapphire laser at 800 nm wavelength. Each pulse had a spot size of 38 mm (1/e2) and a duration of 100 fs. Laser energy was varied between 3.5 and 0.2 mJ resulting in a maximum laser intensity with at least 1014 W/cm2. This reproduces well the spatial and temporal conditions of natural micrometeoroid impacts. 10 shots per applied laser energy were executed with a spacing of at least 100 mm to avoid an overlap of the affected areas. The recovered material was investigated with SEM and TEM. Sample preparation for TEM was done with focused ion beam (FIB) technique by cutting 100 nm thin lamellae perpendicular to the irradiated surface. Results: The laser single shots produced mainly spherical to partly irregular shaped microcraters with a distinct melt layer in typical ejecta morphology at the rims. The samples parallel to (001) and (210) show strong fracturing at the crater surfaces, subordinately also the (100) cut sample. There is a correlation between fracture density and laser energy. The craters produced on the (001) plane have cracks mainly subparallel to the traces of the cleavage planes on {210} and (100) with smaller subspherical cracks at the crater rim. The fractures of the (210) sample show a preferred orientation parallel to the [001] direction. The fractures of the (100) sample are mainly subparallel to [010] and [001]. The samples parallel to the (010), (301) and (211) planes do not show fractures at the crater surfaces. TEM investigations of the craters reveal a layered structure independent of the sample orientation. From top to bottom there is a glass layer, a dominant mechanically deformed layer containing shock defects and the undeformed substrate. All samples show parallel planar lamellae, that are amorphous in the upper part of the deformed layer and become thinner towards the bottom until they turn to microfractures or stacking faults. At the interface to the glass layer there are always two conjugated directions of the amorphous features, which have an angle of 30-50° to the surface normal. Deeper in the deformed layer the samples have either domains with subparallel lamellae in different orientations, or the layer contains homogeneously lamellae with one dominant or two conjugated directions. Activated cleavage planes can only be observed in the (210) sample, where the lamellae are parallel to the (100) cleavage. The transformation to clinoenstatite can be seen in the (301) sample. It occurs in the lower part of the deformed layer associated with microfractures and dislocations. Discussion and future work: The main deformation features in our shocked enstatite are microfractures and lamellae that probably act as shear planes. Frictional heating along this shear planes leads to amorphization. These experimentally produced structures are in good agreement with observations in natural samples like the Martian Meteorite Allan Hills 84001 [6]. We did not observe the formation of iron nanoparticles, which are the cause for the spectral darkening and reddening in naturally space weathered pyroxene [5] or have been observed in other experimentally irradiated pyroxene powder pellets [7]. Further experiments are therefore intended to be performed with a more Fe rich enstatite.

Published
2018

44. Orientation of Planar Deformation Features (PDFs) in quartz

Author

Langenhorst, F and Deutsch, A

Subjects
Solid-State Physics
Abstract

Differently oriented single crystal quartz was shocked experimentally at pressures of 20 to 32 GPa and pre-shock temperatures up to 630 C. Based on this systematic investigation, we can demonstrate that the orientation of planar deformation features in quartz is not only dependent on shock pressure but also on pre-shock temperature and shock direction. Moreover, the orientation of Planar Deformation Features (PDF's) is strongly influenced by the set-up in recovery experiments. PDF's in quartz are defined as optically recognizable, planar microstructures diagnostically produced by shock compression. PDF's differ from all kinds of microstructures found in volcanic environment and therefore, their presence is a primary criterion for recognizing impact craters and ejecta layers such as the K/T boundary. Because experiments have shown a pressure dependence of the orientation of PDF's, this property is used extensively for shock wave barometry in natural impact sites. However, the unreflected application of experimental results neglects that parameters such as pre-shock temperature, shock direction, or the experimental arrangement may influence the spatial distribution of PDF's. In order to test this assumption, shock experiments on single crystal quartz at pre-shock temperatures of 20, 275, 540, and 630 C, and with shock directions (1010) and (0001) were performed. Most of the recovery experiments were carried out by using a reverberation technique, whereas in only one experiment a single shock was produced (impedance method). In the former case 0.5 mm thin discs of single crystal quartz were used, in the latter a 15 mm thick cylinder. The orientation of PDF's was measured by means of a conventional universal stage and the results are given. Effects of the experimentation technique can be derived showing the orientation of PDF's in quartz shocked at 27.5 GPa. In comparison to the well defined peaks at (1012) found in samples from reverberation experiments, the impedance matching technique causes PDF's with a broad distribution pattern and indistinct maxima. Our results have serious implications for shock-wave barometry in nature: the existing classification scheme which relates PDF orientation exclusively to shock pressure is no longer applicable. In consequence more experimental data is needed.

Published
1993

45. Influence of the preshock temperature on shock effects in quartz

Author

Langenhorst, F and Deutsch, A

Subjects
Geophysics
Abstract

Shock metamorphic features are the prime indicators for recognizing impact phenomena on Earth and other planetary bodies. Although the pressure dependence of shock features is well known, information about the influence of the preshock temperature is almost lacking. Especially in the case of large-scale impacts like Sudbury, it is expected that deep-seated crustal rocks were subjected to shock at elevated temperatures. Therefore, we continued to perform shock experiments at elevated temperatures on less than 0.5-mm thin disks of single crystal quartz cut parallel to the (1010) face. All recovered quartz samples were investigated by universal stage, spindle stage, and a newly developed density gradient technique. Errors of refractive index and density measurements are +/- 0.0005 and +/- 0.002 g/cu cm respectively. Our investigations indicate that shock metamorphic features are strongly dependent on the preshock temperature. This statement has far-reaching implications with respect to shock wave barometry that is based on data from recovery experiments at room temperature. These datasets might be applicable only to low-temperature target rocks. Moreover, this study demonstrates that shock recovery experiments are definitely required for understanding the complete pressure-temperature regime of shock metamorphism on planetary bodies.

Published
1992

47. Surface structural transformation of sintered alumina induced by excimer laser irradiation.

Author

Dupas-Bruzek, C., Laude, L. D., Langenhorst, F., and Kolev, K.

Subjects
ALUMINUM oxide, EXCIMER lasers
Abstract

Laser surface processing of ceramics is important for several structural, tribological, optical and electronic applications. However, little is known on the transformation mechanism of alumina under excimer laser irradiation. In this work, a sintered alumina type was typically irradiated at 0.8 J cm[sup -2] and cooled at two drastically different rates. Optical investigations on the irradiated specimens allow to conclude that the amount of transformation products is very much dependant on the cooling rates. Transmission electron microscopy observations show that the transformation product is constituted of an amorphous matrix in which are embedded either (i) copper grains (size up to 1 µm) in slowly cooled samples or (ii) smaller copper or CuAl[sub 2]O[sub 4] spinel grains (size up to 100 nm) in rapidly cooled samples. The cement that is present in the starting material at grain boundaries is found to play an important role on the formation of the new amorphous or crystalline materials. All the copper grains exhibit a 〈120〉 common zone axis perpendicular to the irradiated surface and parallel to the bulk-to-surface thermal gradient, which drives that preferred orientation. These results reveal the details of the phenomenology of the laser-induced material transformation. This latter decomposes into (i) the incipient formation of tiny γ-Al[sub 2]O[sub 3] nuclei, (ii) integration of Cu ions present in the melt into these tiny γ-Al[sub 2]O[sub 3] nuclei that transform into CuAl[sub 2]O[sub 4] spinel, and (iii) further sedimentation of Cu ions onto the resulting spinel grains acting as nucleation centers and finally formation of larger copper-rich grains. The minimum nucleation rate of crystalline grains is estimated to be equal to 10[sup 24] cm[sup -3] s[sup -1], while the growth rate is of the order of 0.1 m s[sup -1] in both samples. Both bulk thermal diffusive and convective transports control the transformation of matter. [ABSTRACT FROM AUTHOR]

Published
2003
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