Speciation and thermodynamic properties of manganese(II) chloride complexes in hydrothermal fluids: In situ XAS study

Fe isotope fractionation during phase separation in the NaCl–H2O system: An experimental study with implications for seafloor hydrothermal vents

“…An example of this is provided by XAS studies at supercritical conditions of cobalt chloro-complexes, which indicate that at a similar high temperature (440 • C), the water rich [CoCl 2 (H 2 O) 2 ] 0 complex is predominant at low salinity (<0.5 mol/kg dissolved Cl), whereas [CoCl 4 ] 2− exists at high salinity (Liu et al, 2011). Similar spectroscopic studies for the NiCl 2 -, CdCl 2 -, and MnCl 2 -H 2 O-NaCl systems (Bazarkina et al, 2010;Migdisov et al, 2011;Tian et al, 2012Tian et al, , 2014 also exhibit increasing degrees of stability for tetrahedrally coordinated metal aquo-chloro-complexes at elevated temperatures with analogous changes in coordination chemistry as a function of dissolved chloride concentration. We infer from previous spectroscopic efforts that the chloride-rich liquid phase is dominated by [FeCl 4 ] 2− at all times of the experiment, whereas the vapor phase is susceptible to changes in the relative abundance of [FeCl 2 (H 2 O) 2 ] 0 and [FeCl 4 ] 2− upon progressive phase separation.…”

Zinc complexation in chloride-rich hydrothermal fluids (25–600 °C): A thermodynamic model derived from ab initio molecular dynamics

“…Solutions were measured using a custom-built high pressure (pressure stability better than one bar; accuracy within 5 bar; Bruyère et al, 2008), high temperature (stability better than 1°C; accuracy 5-10°C) autoclave (Testemale et al, 2005). The set-up and analytical procedure was as described for example in Tian et al (2014).…”

“…Ab initio XANES simulations were conducted with the Finite Difference Method using the FDMNES software (Joly, 2001), following the procedure outlined in recent metal complexes studies (Tian et al, 2012(Tian et al, , 2014. To compare to the experimental spectra, the calculated raw spectra (photo-absorption cross-sections) were convoluted with a Lorentzian function of energy-dependent width to reproduce the core-hole lifetime broadening and the inelastic Plasmon interactions with the photoelectron; the width of the function varies from 1.67 eV at the Zn K-edge (corehole life time) to $15 eV at 100 eV above the edge.…”

Speciation and thermodynamic properties of zinc in sulfur-rich hydrothermal fluids: Insights from ab initio molecular dynamics simulations and X-ray absorption spectroscopy

“…Helium was used as a pressure medium. The set-up, temperature calibration, and analytical procedures were as described for example in Liu et al (2011aLiu et al ( , 2014 and Tian et al (2014).…”

“…Compared to some other divalent metal ions such as Cd (II) (Bazarkina et al, 2010), Fe(II) (Testemale et al, 2009), Mn(II) (Tian et al, 2014), Ni(II) and Co (II) (Liu et al, 2011), a unique feature of Zn(II) bisulfide and chloride complexing is that the only octahedral complex in the system is the aqua Zn(H 2 O) 6 2+ complex; i.e., substitution of a chloride or bisulfide ligand causes the complex to attain a tetrahedral geometry. For example, in the simulations that started with octahedral [Zn(HS) (H 2 O) 5 ] + (simulation 1a, 2a, 4a), this octahedral complex rapidly (within less than 1 ps) lost two water molecules to form tetrahedral [Zn(HS)(H 2 O) 3 ] + .…”