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Zeolites and Negative Thermal Expansion. Rachel Pallant , Josie Paton, Alen Akhabaev , Ross Davies. Zeolites. Microporous Minerals Microporous – Contains pores with diameters <2nm Mineral – Naturally occurring substance that is a stable solid rtp 206 structures identified

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zeolites and negative thermal expansion

Zeolites and Negative Thermal Expansion

Rachel Pallant, Josie Paton,

AlenAkhabaev, Ross Davies

zeolites
Zeolites
  • Microporous Minerals
    • Microporous – Contains pores with diameters <2nm
    • Mineral – Naturally occurring substance that is a stable solid rtp
  • 206 structures identified
  • Base SinO2n, other molecules can be included
negative thermal expansion
Negative Thermal Expansion
  • Caused by decrease in bond angles
  • With no/little energy bond angle is 180°
  • Energy provided by heat overcomes electrostatic forces of electron groups mutually repelling
  • Molecule bends, Si-Si distance now smaller although bonds are longer
zeolites chosen
Zeolites chosen
  • Control – MEP
  • Positive thermal expansion – DON
  • Negative thermal expansion – EDI, YUG
  • Detail - STI
mep 1104 atoms
MEP (1104 atoms)
  • Already proven to have negative thermal expansion
don 1152 atoms
DON (1152 atoms)
  • Was modelled to have positive thermal expansion
edi 1872 atoms
EDI (1872 atoms)
  • Was modelled to have negative thermal expansion
yug 2160 atoms
YUG (2160 atoms)
  • Was modelled to have negative thermal expansion
sti 2592 atoms
STI (2592 atoms)
  • Showed an unusual shift
sti detail 1728 atoms
STI Detail (1728 atoms)
  • Using smaller temperature steps still just showed a sudden shift
  • Only two of the side lengths changed, not all three
sti structure animation
STI Structure Animation
  • Structure of STI at 90K
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