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Title: The mechanism of the area negative thermal expansion in KBe{sub 2}BO{sub 3}F{sub 2} family crystals: A first-principles study

A very recent study demonstrated that the KBe{sub 2}BO{sub 3}F{sub 2} (KBBF) family of crystals, including KBBF, RbBe{sub 2}BO{sub 3}F{sub 2}, and CsBe{sub 2}BO{sub 3}F{sub 2}, are the only known borates exhibiting a rarely occurring isotropic area negative thermal expansion (NTE) behavior, over a very large temperature range. In the present work, the NTE mechanism in these crystals is comprehensively investigated using the first-principles calculations. It is revealed that the area NTE behavior mainly originates from the concerted distortion of [BeO{sub 3}F] tetrahedra in the two-dimensional [Be{sub 2}BO{sub 3}F{sub 2}]{sub ∞} framework with respect to temperature, while the [BO{sub 3}] triangles remain almost rigid. Moreover, the different magnitude of NTE effect in the three crystals is attributed to the interaction difference between the alkali metal atoms (K, Rb, or Cs) and the [Be{sub 2}BO{sub 3}F{sub 2}]{sub ∞} layer.
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ; ; ;  [1]
  1. Center for Crystal Research and Development, Key Lab of Functional Crystals and Laser Technology of Chinese Academy of Sciences, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190 (China)
  2. (China)
  3. Laboratory of Crystal Physics, Kirensky Institute of Physics, SB RAS, Krasnoyarsk 660036 (Russian Federation)
  4. (Russian Federation)
  5. School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan 430074 (China)
  6. Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002 (China)
Publication Date:
OSTI Identifier:
22494998
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 119; Journal Issue: 5; Other Information: (c) 2016 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ALKALI METALS; BERYLLIUM OXIDES; BORATES; CRYSTALS; LAYERS; THERMAL EXPANSION; TWO-DIMENSIONAL SYSTEMS