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Title: Negative-pressure polymorphs made by heterostructural alloying

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 2x to 4x lower electron effective mass compared to MnSe and MnTe parent compounds and has a piezoelectric response that none of the parent compounds have. Lastly, this example shows how heterostructural alloying can lead to negative-pressure polymorphs with useful properties - materials that are otherwise nearly impossible to make.
Authors:
ORCiD logo [1] ; ORCiD logo [2] ; ORCiD logo [3] ; ORCiD logo [4] ; ORCiD logo [4] ; ORCiD logo [1] ;  [1] ; ORCiD logo [1] ; ORCiD logo [4] ; ORCiD logo [3] ; ORCiD logo [1] ; ORCiD logo [1] ; ORCiD logo [1]
  1. National Renewable Energy Lab. (NREL), Golden, CO (United States)
  2. National Renewable Energy Lab. (NREL), Golden, CO (United States); Univ. of Colorado, Boulder, CO (United States)
  3. Univ. of Connecticut, Storrs, CT (United States)
  4. SLAC National Accelerator Lab., Menlo Park, CA (United States)
Publication Date:
Report Number(s):
NREL/JA-5K00-68342
Journal ID: ISSN 2375-2548
Grant/Contract Number:
AC36-08GO28308; AC02-76SF00515
Type:
Accepted Manuscript
Journal Name:
Science Advances
Additional Journal Information:
Journal Volume: 4; Journal Issue: 4; Journal ID: ISSN 2375-2548
Publisher:
AAAS
Research Org:
National Renewable Energy Lab. (NREL), Golden, CO (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); USDOE Office of Energy Efficiency and Renewable Energy (EERE) USDOE Laboratory Directed Research and Development (LDRD)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; polymorphism; synthesis; crystal structure
OSTI Identifier:
1437565
Alternate Identifier(s):
OSTI ID: 1438818