Epsomite, MgSO47H2O, is a widespread evaporite mineral on Earth, and on Mars too, as well as being a candidate rock-forming mineral inside the icy moons of the outer solar system [1]. Many spectroscopic, thermal and diffractometric studies have recently been undertaken to study the structural, thermodynamical and thermal stability of the salts of the MgSO4•nH2O series, epsomite included, under different environmental conditions of relative humidity, pressure and temperatures. In this work X-Ray single crystal diffraction has been used to study the structure of epsomite at 298K, 175K and 102K, respectively, in order to 1) describe the structure of epsomite at low temperature 2) systematically describe changes that occur in the epsomite structure at low temperature considering polyhedral geometries (bond distances, bond angles) and hydrogen bonds variations 3) justify with structural evidences the observed changes that occur in this structure with changing temperatures. Single-crystal X-ray data collected on a Nonius Kappa CCD diffractometer (MoKα radiation) were refined in the space group P212121 using Shelx-97. (a= 11.8829(2), b=11.9984(2), c=6.86230(10), V= 978.40(3) Å3 at 298K; a=11.8796(2), b=11.9571(3), c=6.8203(10), V= 968.79 Å3 at 175K; a=11.8944(2), b=11.9315(2), c=6.80530(10) and V= 965.79(3) Å3 at 102K). Our results show that the hydrogen bonds in this structure get stronger or weaker depending on the necessity by the tetrahedral oxygen atoms to adjust their charge saturation. The polyhedrons, which behave as rigid bodies, tilt to compensate for these bond lengths adjustments. The non-bonded distances seem to be strongly influenced by these adjustments and their trends reflect the behavior of unit cell parameters. The non bonded distances with a prevalent parallel component along the b- and c-axis decrease with decreasing temperature while the one parallel to the a-axis either increase or remain constant with decreasing temperature. References [1] Fortes, A. D. (2005) Axis 1(9), 1-28:

SINGLE CRYSTAL X-RAY DIFFRACTION STUDY OF EPSOMITE AT 298K, 175K AND 102K

CRUCIANI, Giuseppe;MARTUCCI, Annalisa
2010

Abstract

Epsomite, MgSO47H2O, is a widespread evaporite mineral on Earth, and on Mars too, as well as being a candidate rock-forming mineral inside the icy moons of the outer solar system [1]. Many spectroscopic, thermal and diffractometric studies have recently been undertaken to study the structural, thermodynamical and thermal stability of the salts of the MgSO4•nH2O series, epsomite included, under different environmental conditions of relative humidity, pressure and temperatures. In this work X-Ray single crystal diffraction has been used to study the structure of epsomite at 298K, 175K and 102K, respectively, in order to 1) describe the structure of epsomite at low temperature 2) systematically describe changes that occur in the epsomite structure at low temperature considering polyhedral geometries (bond distances, bond angles) and hydrogen bonds variations 3) justify with structural evidences the observed changes that occur in this structure with changing temperatures. Single-crystal X-ray data collected on a Nonius Kappa CCD diffractometer (MoKα radiation) were refined in the space group P212121 using Shelx-97. (a= 11.8829(2), b=11.9984(2), c=6.86230(10), V= 978.40(3) Å3 at 298K; a=11.8796(2), b=11.9571(3), c=6.8203(10), V= 968.79 Å3 at 175K; a=11.8944(2), b=11.9315(2), c=6.80530(10) and V= 965.79(3) Å3 at 102K). Our results show that the hydrogen bonds in this structure get stronger or weaker depending on the necessity by the tetrahedral oxygen atoms to adjust their charge saturation. The polyhedrons, which behave as rigid bodies, tilt to compensate for these bond lengths adjustments. The non-bonded distances seem to be strongly influenced by these adjustments and their trends reflect the behavior of unit cell parameters. The non bonded distances with a prevalent parallel component along the b- and c-axis decrease with decreasing temperature while the one parallel to the a-axis either increase or remain constant with decreasing temperature. References [1] Fortes, A. D. (2005) Axis 1(9), 1-28:
2010
SINGLE CRYSTAL X-RAY DIFFRACTION; EPSOMITE; low temperature
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11392/1402704
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