Negative-Pressure Polymorphs Made by Heterostructural Alloying

Andriy Zakutayev, Philip Parilla, William Tumas, Stephan Lany, James Steffes, Bryan Huey, Laura Schelhas, Kevin Stone, Michael Toney, Sebastian Siol, Aaron Holder, Lauren Garten, John Perkins

Research output: Contribution to journalArticlepeer-review

35 Scopus Citations

Abstract

The ability of a material to adopt multiple structures, known as polymorphism, is a fascinating natural phenomenon. Various polymorphs with unusual properties are routinely synthesized by compression under positive pressure. However, changing a material’s structure by applying tension under negative pressure is much more difficult. We show how negative-pressure polymorphs can be synthesized by mixing materials with different crystal structures—a general approach that should be applicable to many materials. Theoretical calculations suggest that it costs less energy to mix low-density structures than high-density structures, due to less competition for space between the atoms. Proof-of-concept experiments confirm that mixing two different high-density forms of MnSe and MnTe stabilizes a Mn(Se,Te) alloy with a low-density wurtzite structure. This Mn(Se,Te) negative-pressure polymorph has 2× to 4× lower electron effective mass compared to MnSe and MnTe parent compounds and has a piezoelectric response that none of the parent compounds have. This example shows how heterostructural alloying can lead to negative-pressure polymorphs with useful properties—materials that are otherwise nearly impossible to make.

Original languageAmerican English
Article numbereaaq1442
Number of pages7
JournalScience Advances
Volume4
Issue number4
DOIs
StatePublished - 2018

Bibliographical note

Publisher Copyright:
Copyright © 2018 The Authors.

NREL Publication Number

  • NREL/JA-5K00-68342

Keywords

  • crystal structure
  • polymorphism
  • synthesis

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