@article{SpiekermannWilkeJahn2016,
  author    = {Spiekermann, Georg and Wilke, Max and Jahn, Sandro},
  title     = {Structural and dynamical properties of supercritical H2O-SiO2 fluids studied by ab initio molecular dynamics},
  series = {Chemical geology : official journal of the European Association for Geochemistry},
  volume    = {426},
  journal   = {Chemical geology : official journal of the European Association for Geochemistry},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0009-2541},
  doi       = {10.1016/j.chemgeo.2016.01.010},
  pages     = {85 -- 94},
  year      = {2016},
  abstract  = {In this study we report the structure of supercritical H2O-SiO2 fluid composed of 50 mol\% H2O and 50 mol\% SiO2 at 3000 K and 2400 K. investigated by means of ab initio molecular dynamics of models comprising 192 and 96 atoms. The density is set constant to 138 g/cm(3), which yields a pressure of 4.3 GPa at 3000 K and 3.6 GPa at 2400 K. Throughout the trajec[ories, water molecules are formed and dissociated via the network modifying reaction 2 SiOH = SiOSi + H2O The calculation of the reaction constant K- [OH](2)/[H2O][O2-] is carried out on the basis of the experimentally relevant Q ' species notation and agrees well with an extrapolation of experimental data to 3000 K. After quench from 3000 K to 2400 K, the degree of polymerization of the silicate network in the 192-atom models increases noticeably within several tens of picoseconds, accompanied by release of molecular H2O. An unexpected opposite trend is observed in smaller 96-atom models, due to a finite size effect, as several uncorrelated models of 192 and 96 atoms indicate. The temperature-dependent slowing down of the H2O-silica interaction dynamics is described on the basis of the bond autocorrelation function. (C) 2016 Elsevier B.V. All rights reserved.},
  language  = {en}
}
@article{GruenebergerSchmidtJahnetal.2016,
  author    = {Gr{\"u}neberger, Anja Maria and Schmidt, Christian and Jahn, Sandro and Rhede, Dieter and Loges, Anselm and Wilke, Max},
  title     = {Interpretation of Raman spectra of the zircon-hafnon solid solution},
  series = {European journal of mineralogy},
  volume    = {28},
  journal   = {European journal of mineralogy},
  publisher = {Schweizerbart},
  address   = {Stuttgart},
  issn      = {0935-1221},
  doi       = {10.1127/ejm/2016/0028-2551},
  pages     = {721 -- 733},
  year      = {2016},
  abstract  = {Zircon (ZrSiO4), hafnon (HfSiO4) and five intermediate compositions were synthesized from a Pb silicate melt. The resulting crystals were 20-300 mu m in size and displayed sector and growth zoning. Raman spectra were acquired at locations in the sample for which preceding electron microprobe (EMP) analyses revealed sufficient compositional homogeneity. The dataset documents shifts of Raman bands with changing composition. In this study, bands that have previously not been reported were found for the intermediate compositions and for pure hafnon, in particular at wavenumbers less than 200 cm(-1). For these external modes, the dataset provides new insight into the compositional dependence of their frequencies. Density-functional theory calculations support the observations and are used for a detailed interpretation of the spectra. The pitfalls of the EMP analysis along the zircon-hafnon join are highlighted.},
  language  = {en}
}