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Title: High pressure–low temperature phase diagram of barium: Simplicity versus complexity

Barium holds a distinctive position among all elements studied upon densification. Indeed, it was the first example shown to violate the long-standing notion that high compression of simple metals should preserve or yield close-packed structures. From modest pressure conditions at room temperature, barium transforms at higher pressures from its simple structures to the extraordinarily complex atomic arrangements of the incommensurate and self-hosting Ba-IV phases. By a detailed mapping of the pressure/temperature structures of barium, we demonstrate the existence of another crystalline arrangement of barium, Ba-VI, at low temperature and high pressure. The simple structure of Ba-VI is unlike that of complex Ba-IV, the phase encountered in a similar pressure range at room temperature. First-principles calculations predict Ba-VI to be stable at high pressure and superconductive. The results illustrate the complexity of the low temperature-high pressure phase diagram of barium and the significant effect of temperature on structural phase transformations.
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [4] ; ;  [6]
  1. Laboratoire de Physique des Solides Denses, Université d'Ottawa, Ottawa, Ontario K1N 6N5 (Canada)
  2. Department of Physics and Engineering Physics, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5B2 (Canada)
  3. (China)
  4. SPring-8/JASRI, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan)
  5. (Japan)
  6. State Key Laboratory of Superhard Materials, Jilin University, 130012 Changchun (China)
Publication Date:
OSTI Identifier:
22486151
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 107; Journal Issue: 22; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; BARIUM; COMPRESSION; MAPPING; PHASE DIAGRAMS; PHASE TRANSFORMATIONS; PRESSURE RANGE MEGA PA 10-100; TEMPERATURE RANGE 0273-0400 K; YIELDS