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

Schmuttenmaer, Charles A.

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https://hdl.handle.net/2142/100844 Copy

Description

Title

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

Author(s)

Schmuttenmaer, Charles A.

Contributor(s)

• Williams, Michael R. C.
• Regan, Kevin P.
• Nemes, Coleen T.
• Neu, Jens

Issue Date

2018-06-20

Keyword(s)

Mini-symposium: Far-Infrared Spectroscopy

Abstract

DL-Norvaline is a molecular crystal at room temperature and it undergoes a phase transition when cooled below 190 K. This phase transition is believed to be Martensitic. We investigate this phase transition by measuring its terahertz (THz) spectrum over a range of temperatures. Temperature-dependent THz time-domain spectroscopy (THz-TDS) measurements reveal that the transition temperature (Tβ→α) is 190 K. The influence of nucleation seeds was analyzed by determining the Tβ→α of molecular crystals with varying grain size. Grains of 5 µm or less result in a lower transition temperature (Tβ→α = 180 K) compared to larger grains of 125–250 µm (Tβ→α = 190 K). Additionally, we gain insight into the physical process of the phase transition via temperature-dependent THz-TDS spectra of doped and mixed molecular crystals. The addition of molecular dopants, which differ from DL-norvaline only at the end of the side chain which resides in the hydrophobic layers of the crystal, decreases Tβ→α. This is consistent with a solid-solid phase transition in which the unit cell shifts along this hydrophobic layer, and it leads us to believe that the phase transition in DL-norvaline is Martensitic in nature.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

eng

Permalink

http://hdl.handle.net/2142/100844

DOI

10.15278/isms.2018.WI05

Copyright and License Information

Copyright 2018 Charles A. Schmuttenmaer

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