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See: Gemstone like compound#Carbons versatility

sp3 allotropes:

  • Diamond (cubic)
  • Lonstaleite (hexagonal)
  • ...

sp2 allotropes:

  • Buckyballs (convex curvature; concave from inside) – weak molecular solids
  • Nanotubes (no curvature – flat rolled)
  • 3D meshes (hyperbolic curvature)
  • "penta graphene" (cairo pattern)
  • ...

Binary compounds:

  • Silicon carbide SiC aka moissanite
  • carbon nitrides: beta carbon nitride and cubic gauche carbon nitride

  • Titanium carbide TiC aka titanium-khamrabaevite (cubic rock salt structure) Mohs 9-9.5 refractory
  • Vanadium carbide VC (vanadium is not too common) vanadium-khamrabaevite
    similar is: NbC and TaC (Nb is not abundant, Ta is extremely rare)
  • Zirconium cabide ZrC [1] (same structure but no natural mineral present)
    similar is: HfC (Hf is pretty rare)
  • Iron carbide (this here is not cementite!!) iron-khamrabaevite (unknown stability, likely very hard)

  • Chromium_carbide (various stoichiometric & structures - may point to useful covalent behavior)
    Cr3C2 Tongbaite (refractory, Mohs 9.6; orthorhombic; 6.64g/ccm) Cr is not too abundant
  • Molybdenium carbide (de) Mo2C (insoluble, two modifications α and β) Mo is rather rare
  • Tungsten_carbide (hexagonal, Mohs 9) W is rather rare

  • Fe3C, Ni3C, Co3C cohenite endmembers (likely rather metallic, Mohs 5.5-6)

  • copper and zinc are more electronegative => more covalent behavior => organometallic compounds

  • Boron carbide B4C [2] (boron is not too common)
  • Aluminium carbide [3] (reacts with water - releases methane gas CH4)
  • Beryllium carbide Be2C (very hard but reactive, toxic and rare)
  • Magnesium carbide ???
  • Calcium carbide CaC2 (an acetylide - reacts with water - releases ethyne gas C2H2)
  • TODO: La, Ce, (Li, Na, K)


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