@article{WunderKutzschbachHosseetal.2018,
  author    = {Wunder, Bernd and Kutzschbach, Martin and Hosse, Luisa and Wilke, Franziska Daniela Helena and Schertl, Hans-Peter and Chopin, Christian},
  title     = {Synthetic B-[4]-bearing dumortierite and natural B-[4]-free magnesiodumortierite from the Dora-Maira Massif},
  series = {European journal of mineralogy},
  volume    = {30},
  journal   = {European journal of mineralogy},
  number    = {3},
  publisher = {Schweizerbart},
  address   = {Stuttgart},
  issn      = {0935-1221},
  doi       = {10.1127/ejm/2018/0030-2742},
  pages     = {471 -- 483},
  year      = {2018},
  abstract  = {Dumortierite was synthesized in piston-cylinder experiments at 2.5-4.0 GPa, 650-700 degrees C in the Al2O3 -B2O3-SiO2-H2O (ABSH) system. Electron-microprobe (EMP) analyses reveal significant boron-excess (up to 0.26 B-[4] per formula unit, pfu) and silicon-deficiency relative to the ideal anhydrous dumortierite stoichiometry Al7BSi3O18 . The EMP data in conjunction with results from single-crystal Raman spectroscopy and powder X-ray diffraction provide evidence that silicon at the tetrahedral site is replaced by excess boron via the substitution Si-[4] <--> B-[4] + H. The Raman spectrum of synthetic dumortierite in the frequency region 2000 4000 cm(-1) comprises eight bands, of which six are located at frequencies below 3400 cm(-1). This points to strong hydrogen bonding, most likely O2-H center dot center dot center dot O7 and O7-H center dot center dot center dot O2, arising from a high number of octahedral vacancies at the All site and substitution of trivalent Al3+ and B3+ for Si4+ at Si1 and Si2 sites, causing decreasing acceptor-donor distances and lower incident valence at the acceptor oxygen. Contrary to the synthetic high-pressure ABSH-dumortierite, magnesiodumortierite from the Dora-Maira Massif, which is assumed to have formed at similar conditions (2.5-3.0 GPa, 700 degrees C), does not show any B-excess. Tourmaline shows an analogous behaviour in that magnesium-rich (e.g., dravitic) tourmaline formed at high pressure shows no or only minor amounts of tetrahedral boron, whereas natural aluminum-rich tourmaline and synthetic olenitic tourmaline formed at high pressures can incorporate significant amounts of tetrahedral boron. Two mechanisms might account for this discrepancy: (i) Structural avoidance of Mg-[6]-(OR3+)-R-[4] configurations in magnesiodumortierite due to charge deficieny at the oxygens O2 and O7 and strong local distortion of M1 due to decreased O2-O7 bond length, and/or (ii) decreasing fluid mobility of boron in Al-rich systems at high pressures.},
  language  = {en}
}
@article{KutzschbachWunderKrstulovicetal.2016,
  author    = {Kutzschbach, Martin and Wunder, Bernd and Krstulovic, Marija and Ertl, Andreas and Trumbull, Robert B. and Rocholl, Alexander and Giester, Gerald},
  title     = {First high-pressure synthesis of rossmanitic tourmaline and evidence for the incorporation of Li at the X site},
  series = {Physics and chemistry of minerals / in cooperation with the International Mineralogical Association (IMA)},
  volume    = {44},
  journal   = {Physics and chemistry of minerals / in cooperation with the International Mineralogical Association (IMA)},
  publisher = {Springer},
  address   = {New York},
  issn      = {0342-1791},
  doi       = {10.1007/s00269-016-0863-0},
  pages     = {353 -- 363},
  year      = {2016},
  abstract  = {Lithium is an important component of some tourmalines, especially in chemically evolved granites and pegmatites. All attempts at synthesizing Li-rich tourmaline have so far been unsuccessful. Here we describe the first synthesis of rossmanitic tourmaline at 4 GPa and 700 degrees C in the system Li2OAl2O3SiO2B2O3H2O (LASBH) from seed-free solid starting materials consisting of a homogenous mixture of Li2O, gamma-Al2O3, quartz and H3BO3. The solid run products after 12-day run duration comprise rossmanitic tourmaline (68 wt\%), dumortierite (28 wt\%) and traces of spodumene (3 wt\%) and coesite (1 wt\%). Tourmaline forms idiomorphic, large prismatic crystals (30 X 100 mu m), which are inclusion free and chemically unzoned. The refined cell dimensions of the tourmaline are: a = 15.7396(9) angstrom, c = 7.0575(5) angstrom, V = 1514.1(2) angstrom 3. Conventionally, the Li+ ion is assumed to exclusively occupy the octahedral Y site in the tourmaline structure to a maximum of 2 Li per formula unit (pfu). However, the chemical composition of our synthetic tourmaline determined by electron microprobe and secondary ion mass spectroscopy results in the formula: (X)(square Li-0.67(11)(0.33(11)))(Y)(Al2.53(10)Li0.47(10))(Z)(Al-6)T(Si5.42(15)B0.58(15))O-18(B)(BO3)(3)(V+W)[(OH)(2.40(3))O-1.60(3)], wherein a significant amount of Li occupies the X site for charge balance requirements. Reliable assignment of the OH-stretching vibrations in a polarized single-crystal Raman spectrum such as a single-crystal XRD structure refinement, confirms the incorporation of Li at the X site [0.24(9) and 0.15(5) Li-X pfu, respectively]. The SREF data show that the LiO1 distances are shortened significantly in order to compensate for the smaller ionic radius of Li+ compared to Na+, K+ or Ca2+ at the X site, i.e., Li is closer to the Si6O18 ring and to a sevenfold coordination with oxygen.},
  language  = {en}
}
@article{KutzschbachGuttmannMarquardtetal.2018,
  author    = {Kutzschbach, Martin and Guttmann, Peter and Marquardt, K. and Werner, S. and Henzler, K. D. and Wilke, Max},
  title     = {A transmission x-ray microscopy and NEXAFS approach for studying corroded silicate glasses at the nanometre scale},
  series = {European journal of glass science and technology / Deutsche Glastechnische Gesellschaft (DGG) and the Society of Glass Technology (SGT). B, Physics and chemistry of glasses},
  volume    = {59},
  journal   = {European journal of glass science and technology / Deutsche Glastechnische Gesellschaft (DGG) and the Society of Glass Technology (SGT). B, Physics and chemistry of glasses},
  number    = {1},
  publisher = {Society of Glass Technology},
  address   = {Sheffield},
  issn      = {1753-3562},
  doi       = {10.13036/17533562.59.1.043},
  pages     = {11 -- 26},
  year      = {2018},
  abstract  = {In this study transmission X-ray microscopy (TXM) was tested as a method to investigate the chemistry and structure of corroded silicate glasses at the nanometer scale. Three different silicate glasses were altered in static corrosion experiments for 1-336 hours at temperatures between 60 degrees C and 85 degrees C using a 25\% HCl solution. Thin lamellas were cut perpendicular to the surface of corroded glass monoliths and were analysed with conventional TEM as well as with TXM. By recording optical density profiles at photon energies around the Na and O K-edges, the shape of the corrosion rim/pristine glass interfaces and the thickness of the corrosion rims has been determined. Na and O near-edge X-ray absorption fine-structure spectra (NEXAFS) were obtained without inducing irradiation damage and have been used to detect chemical changes in the corrosion rims. Spatially resolved NEXAFS spectra at the O K-edge provided insight to structural changes in the corrosion layer on the atomic scale. By comparison to O K-edge spectra of silicate minerals and (hydrous) albite glass as well as to O K-edge NEXAFS of model structures simulated with ab initio calculations, evidence is provided that changes of the fine structure at the O K-edge are assigned to the formation of siloxane groups in the corrosion rim.},
  language  = {en}
}