High-pressure phase transitions in tetrakis(trimethylsilyl)silane Si[Si(CH3)(3)](4)
Författare
Summary, in English
The compound tetrakis(trimethylsilyl)silane S-i[Si(CH3,)(3)](4) (TSi) has been studied at room temperature for pressures up to 2 1.5(1) GPa, using X-ray powder diffraction with synchrotron radiation. Three different phases are reported in the investigated pressure range. The c.c.p.-type structure is stable up to a pressure of 0.19(1) GPa (Fm (3) over barm, a = 13.52110)Angstrom, V = 2471.95(1)Angstrom(3), Z = 4 at 0.02(1)GPa). It shows a severe orientational disorder of the molecules. At pressures 0.19(1)-0.71(1)GPa a monoclinic phase (HP1) is found with space group P2(1)/n and Z=8 (a = 17.746(1)Angstrom, b = 16.098(1)Angstrom, c= 16.871(1)Angstrom, gamma = 111.437(5)degrees and V = 4486.3(8) Angstrom(3) at 0.24(1)GPa). Another monoclinic phase (HP2) exists at pressures 0.52(1)-8.67(5)GPa. This phase has a smaller unit cell than the HP1 phase with Z(.)=2 (a =8.3778(8)Angstrom, b=9.1050(7)Angstrom, c= 13.3024(8)Angstrom, gamma= 111.63(1)degrees and V = 943.22(6) Angstrom(3) at 1.73(2)GPa). The pressure dependencies of the unit-cell volumes are successfully described by Mumaghan or Vinet-type equations of state. The structures at different pressures and temperatures of TSi and related compounds are described as distorted superstructures of the c.c.p. arrangement. The occurrence of different superstructures is rationalized as the result of an optimized packing of ordered molecules of various shapes.
Avdelning/ar
Publiceringsår
2003
Språk
Engelska
Sidor
425-437
Publikation/Tidskrift/Serie
High Pressure Research
Volym
23
Issue
4
Dokumenttyp
Artikel i tidskrift
Förlag
Taylor & Francis
Ämne
- Inorganic Chemistry
Nyckelord
- molecular crystal
- diffraction
- X-ray powder
- tetrakis(trimethylsilyl)silane
- high-pressure
- rotator phase
- plastic crystal
Status
Published
ISBN/ISSN/Övrigt
- ISSN: 1477-2299