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Zeolites and Negative Thermal Expansion

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

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  1. Zeolites and Negative Thermal Expansion Rachel Pallant, Josie Paton, AlenAkhabaev, Ross Davies

  2. 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

  3. 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

  4. Zeolites chosen • Control – MEP • Positive thermal expansion – DON • Negative thermal expansion – EDI, YUG • Detail - STI

  5. MEP (1104 atoms) • Already proven to have negative thermal expansion

  6. DON (1152 atoms) • Was modelled to have positive thermal expansion

  7. EDI (1872 atoms) • Was modelled to have negative thermal expansion

  8. YUG (2160 atoms) • Was modelled to have negative thermal expansion

  9. STI (2592 atoms) • Showed an unusual shift

  10. STI Detail (1728 atoms) • Using smaller temperature steps still just showed a sudden shift • Only two of the side lengths changed, not all three

  11. STI Structure Animation • Structure of STI at 90K

  12. Thank You!

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