Phase diagram of germanium telluride encapsulated in carbon nanotubes from first-principles searches

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  • Jamie Wynn
  • Paolo Medeiros
  • Andrij Vasylenko
  • Jeremy Sloan
  • David Quigley

Colleges, School and Institutes


Germanium telluride has attracted great research interest, primarily because of its phase-change properties. We have developed a general scheme, based on the ab initio random structure searching (AIRSS) method, for predicting the structures of encapsulated nanowires, and using this we predict a number of thermodynamically stable structures of GeTe nanowires encapsulated inside carbon nanotubes of radii under 9 Å. We construct the phase diagram of encapsulated GeTe, which provides quantitative predictions about the energetic favorability of different filling structures as a function of the nanotube radius, such as the formation of a quasi-one-dimensional rock-salt-like phase inside nanotubes of radii between 5.4 and 7.9 Å . Simulated TEM images of our structures show excellent agreement between our results and experimental TEM imagery. We show that, for some nanotubes, the nanowires undergo temperature-induced phase transitions from one crystalline structure to another due to vibrational contributions to the free energy, which is a first step toward nano-phase-change memory devices.


Original languageEnglish
Article number073001(R)
JournalPhysical Review Materials
Publication statusPublished - 26 Dec 2017