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Bulk modulus and high-pressure crystal structures of tetrakis(trimethylsilyl)methane C[Si(CH3)3]4 determined by X-ray powder diffraction

Dinnebier, Robert E.; Carlson, Stefan LU and Van Smaalen, Sander (2000) In Acta Crystallographica. Section B: Structural Science, Crystal Engineering and Materials 56(2). p.310-316
Abstract

The pressure dependence of the crystal structure of cubic tetrakis(trimethylsilyl)methane C[Si(CH3)3]4 (TC) (P <16.0 GPa, T = 298 K) is reported using high-resolution angle-dispersive X-ray powder diffraction. The compound has crystal structures with the molecules in a cubic-close-packed (c.c.p.) arrangement. It shows three phase transitions in the measured pressure range. At ambient conditions, TC has space group Fm3m (Z = 4) with a = 12.8902 (2) Å, V = 2141.8 (1) Å3 (phase I). Between 0 and 0.13 GPa TC exhibits a first-order phase transition into a structure with space group Pa3 (phase II). A second first-order phase transition occurs between 0.2 and 0.28 GPa into a structure with space... (More)

The pressure dependence of the crystal structure of cubic tetrakis(trimethylsilyl)methane C[Si(CH3)3]4 (TC) (P <16.0 GPa, T = 298 K) is reported using high-resolution angle-dispersive X-ray powder diffraction. The compound has crystal structures with the molecules in a cubic-close-packed (c.c.p.) arrangement. It shows three phase transitions in the measured pressure range. At ambient conditions, TC has space group Fm3m (Z = 4) with a = 12.8902 (2) Å, V = 2141.8 (1) Å3 (phase I). Between 0 and 0.13 GPa TC exhibits a first-order phase transition into a structure with space group Pa3 (phase II). A second first-order phase transition occurs between 0.2 and 0.28 GPa into a structure with space group P213 (phase III). Under non-hydrostatic pressure conditions (P > 10 GPa) a transformation is observed into a c.c.p. structure that is different from the face-centred-cubic structure at ambient conditions. A non-linear compression behaviour is observed, which could be described by a Vinet relation in the range 0.28-4.8 GPa. The extrapolated bulk modulus of the high-pressure phase III was determined to be K0 = 7.1 (8) GPa. The crystal structures in phase III are refined against X-ray powder data measured at several pressures between 0.49 and 4.8 GPa, and the molecules are found to be fully ordered. This is interpreted to result from steric interactions between neighbouring molecules, as shown by analysing the pressure dependence of intramolecular angles, torsion angles and intermolecular distances. Except for their cell dimensions, phases I, II and III are found to be isostructural to the corresponding phases at low temperatures.

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published
in
Acta Crystallographica. Section B: Structural Science, Crystal Engineering and Materials
volume
56
issue
2
pages
7 pages
publisher
Wiley-Blackwell
external identifiers
  • Scopus:0038845494
ISSN
0108-7681
language
English
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13791572-8e03-4f43-9542-fc9c65911213
date added to LUP
2016-05-04 11:37:53
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2017-01-01 08:24:37
@article{13791572-8e03-4f43-9542-fc9c65911213,
  abstract     = {<p>The pressure dependence of the crystal structure of cubic tetrakis(trimethylsilyl)methane C[Si(CH<sub>3</sub>)<sub>3</sub>]<sub>4</sub> (TC) (P &lt;16.0 GPa, T = 298 K) is reported using high-resolution angle-dispersive X-ray powder diffraction. The compound has crystal structures with the molecules in a cubic-close-packed (c.c.p.) arrangement. It shows three phase transitions in the measured pressure range. At ambient conditions, TC has space group Fm3m (Z = 4) with a = 12.8902 (2) Å, V = 2141.8 (1) Å<sup>3</sup> (phase I). Between 0 and 0.13 GPa TC exhibits a first-order phase transition into a structure with space group Pa3 (phase II). A second first-order phase transition occurs between 0.2 and 0.28 GPa into a structure with space group P2<sub>1</sub>3 (phase III). Under non-hydrostatic pressure conditions (P &gt; 10 GPa) a transformation is observed into a c.c.p. structure that is different from the face-centred-cubic structure at ambient conditions. A non-linear compression behaviour is observed, which could be described by a Vinet relation in the range 0.28-4.8 GPa. The extrapolated bulk modulus of the high-pressure phase III was determined to be K<sub>0</sub> = 7.1 (8) GPa. The crystal structures in phase III are refined against X-ray powder data measured at several pressures between 0.49 and 4.8 GPa, and the molecules are found to be fully ordered. This is interpreted to result from steric interactions between neighbouring molecules, as shown by analysing the pressure dependence of intramolecular angles, torsion angles and intermolecular distances. Except for their cell dimensions, phases I, II and III are found to be isostructural to the corresponding phases at low temperatures.</p>},
  author       = {Dinnebier, Robert E. and Carlson, Stefan and Van Smaalen, Sander},
  issn         = {0108-7681},
  language     = {eng},
  number       = {2},
  pages        = {310--316},
  publisher    = {Wiley-Blackwell},
  series       = {	Acta Crystallographica. Section B: Structural Science, Crystal Engineering and Materials },
  title        = {Bulk modulus and high-pressure crystal structures of tetrakis(trimethylsilyl)methane C[Si(CH<sub>3</sub>)<sub>3</sub>]<sub>4</sub> determined by X-ray powder diffraction},
  volume       = {56},
  year         = {2000},
}