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Extraordinary Indentation Strain Stiffening Produces Superhard Tungsten Nitrides.

Journal Article


Abstract


  • Transition-metal light-element compounds are a class of designer materials tailored to be a new generation of superhard solids, but indentation strain softening has hitherto limited their intrinsic load-invariant hardness to well below the 40 GPa threshold commonly set for superhard materials. Here we report findings from first-principles calculations that two tungsten nitrides, hP4-WN and hP6-WN_{2}, exhibit extraordinary strain stiffening that produces remarkably enhanced indentation strengths exceeding 40 GPa, raising exciting prospects of realizing the long-sought nontraditional superhard solids. Calculations show that hP4-WN is metallic both at equilibrium and under indentation, marking it as the first known intrinsic superhard metal. An x-ray diffraction pattern analysis indicates the presence of hP4-WN in a recently synthesized specimen. We elucidate the intricate bonding and stress response mechanisms for the identified structural strengthening, and the insights may help advance rational design and discovery of additional novel superhard materials.

Publication Date


  • 2017

Citation


  • Lu, C., Li, Q., Ma, Y., & Chen, C. (2017). Extraordinary Indentation Strain Stiffening Produces Superhard Tungsten Nitrides.. Physical review letters, 119(11), 115503. doi:10.1103/physrevlett.119.115503

Web Of Science Accession Number


Start Page


  • 115503

Volume


  • 119

Issue


  • 11

Abstract


  • Transition-metal light-element compounds are a class of designer materials tailored to be a new generation of superhard solids, but indentation strain softening has hitherto limited their intrinsic load-invariant hardness to well below the 40 GPa threshold commonly set for superhard materials. Here we report findings from first-principles calculations that two tungsten nitrides, hP4-WN and hP6-WN_{2}, exhibit extraordinary strain stiffening that produces remarkably enhanced indentation strengths exceeding 40 GPa, raising exciting prospects of realizing the long-sought nontraditional superhard solids. Calculations show that hP4-WN is metallic both at equilibrium and under indentation, marking it as the first known intrinsic superhard metal. An x-ray diffraction pattern analysis indicates the presence of hP4-WN in a recently synthesized specimen. We elucidate the intricate bonding and stress response mechanisms for the identified structural strengthening, and the insights may help advance rational design and discovery of additional novel superhard materials.

Publication Date


  • 2017

Citation


  • Lu, C., Li, Q., Ma, Y., & Chen, C. (2017). Extraordinary Indentation Strain Stiffening Produces Superhard Tungsten Nitrides.. Physical review letters, 119(11), 115503. doi:10.1103/physrevlett.119.115503

Web Of Science Accession Number


Start Page


  • 115503

Volume


  • 119

Issue


  • 11