skip to main content

Title: Unexpected structural softening of interstitial boron solid solution WB{sub 3+x}

Using first-principles calculations, we reveal an unexpected structural softening in a recently proposed WB{sub 3+x} structural model that tries to explain the X-ray diffraction, high resolution TEM, pressure dependence of the normalized lattice c/a ratio, and hardness experimental results of the synthesized tungsten boride compounds with a nominal composition WB{sub 4}. We show that the interstitial boron in WB{sub 3+x}, which was proposed to strengthen the covalent bonding network, unexpectedly weakens the atomic bonding, resulting in a large reduction of its indentation strength to well below that of WB{sub 3}. This is in direct contradiction to the experimental results showing that synthesized WB{sub 4} is harder than WB{sub 3}. The unusual structural softening is attributed to the unique three-center covalent bonding formed by the interstitial boron atoms that can easily deform under indentation. Our results show that the proposed interstitial boron solid solution WB{sub 3+x} structure is incompatible with experimental results, which calls for further investigations to determine the crystal structure of the synthesized WB{sub 4}.
Authors:
;  [1] ;  [2]
  1. Department of Physics and Astronomy and Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shanghai Jiao Tong University, Shanghai 200240 (China)
  2. Department of Physics and High Pressure Science and Engineering Center, University of Nevada, Las Vegas, Nevada 89154 (United States)
Publication Date:
OSTI Identifier:
22392054
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 105; Journal Issue: 21; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; BORON; COVALENCE; CRYSTAL STRUCTURE; PRESSURE DEPENDENCE; SOLID SOLUTIONS; STRUCTURAL MODELS; TRANSMISSION ELECTRON MICROSCOPY; TUNGSTEN; X-RAY DIFFRACTION