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Exploring the solid state phase transition in dl-norvaline with terahertz spectroscopy.

Jens Neu1, Coleen T Nemes, Kevin P Regan

  • 1Department of Chemistry, Yale University, PO Box 208107, 225 Prospect St., New Haven, CT 06520-8107, USA. jens.neu@yale.edu charles.schmuttenmaer@yale.edu.

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dl-Norvaline exhibits a Martensitic phase transition around 190 K. This molecular crystal

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Area of Science:

  • Solid-state physics
  • Materials science
  • Crystallography

Background:

  • dl-Norvaline is a molecular crystal with potential applications in molecular machines.
  • A phase transition occurs below 190 K, suspected to be Martensitic.
  • Understanding this transition is crucial for its technological applications.

Purpose of the Study:

  • To investigate the Martensitic phase transition in dl-Norvaline.
  • To determine the transition temperature using terahertz spectroscopy.
  • To analyze the influence of crystal properties on the phase transition.

Main Methods:

  • Terahertz time-domain spectroscopy (THz-TDS) was employed.
  • Measurements were conducted over a range of temperatures.
  • Crystal grain size and doping were varied to study their effects.

Main Results:

  • The transition temperature (Tβ→α) was confirmed at 190 K.
  • Smaller grain sizes (≤ 5 μm) lowered the transition temperature to 180 K.
  • Molecular dopants decreased the transition temperature, supporting a solid-solid shift mechanism.

Conclusions:

  • The phase transition in dl-Norvaline is confirmed to be Martensitic.
  • Crystal morphology and doping significantly influence the transition temperature.
  • The findings provide insight into the physical mechanisms of solid-solid phase transitions.