Crystal structure refinements of stoichiometric Ni3Se2 and NiSe

Kohei Unoki, Akira Yoshiasa, Ginga Kitahara, Tadao Nishiayama, Makoto Tokuda, Kazumasa Sugiyama, Akihiko Nakatsuka

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)


Single crystals of Ni3Se2 (trinickel diselenide) and NiSe (nickel selenide) with stoichiometric chemical com­positions were grown in evacuated silica-glass tubes. The chemical com­positions of the single crystals of Ni3Se2 and NiSe were determined by scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM/EDS). The crystal structures of Ni3Se2 [rhombohedral, space group R32, a = 6.02813 (13), c = 7.24883 (16) Å, Z = 3] and NiSe [hexa­gonal, space group P63/mmc, a = 3.66147 (10), c = 5.35766 (16) Å, Z = 2] were analyzed by single-crystal X-ray diffraction and refined to yield R values of 0.020 and 0.018 for 117 and 85 unique reflections, respectively, with F o > 4σ(F o). R32 is a Sohncke type of space group where enanti­omeric structures can exist; the single-domain structure obtained by the refinement was confirmed to be correct by a Flack parameter of-0.05 (2). The existence of Ni-Ni bonds was confirmed in both com­pounds, in addition to the Ni-Se bonds. The value of the atomic displacement parameter (mean-square displacement) of each atom in NiSe was larger than that in Ni3Se2. The larger amplitude of the atoms in NiSe corresponds to longer Ni-Se and Ni-Ni bond lengths in NiSe than in Ni3Se2. The Debye temperatures, θD, estimated from observed mean-square displacements for Ni and Se in Ni3Se2, were 322 and 298 K, respectively, while those for Ni and Se in NiSe were 246 and 241 K, respectively. The existence of large cavities in the structure and the weak bonding force are likely responsible for the brittle and soft nature of the NiSe crystal.

Original languageEnglish
Pages (from-to)169-175
Number of pages7
JournalActa Crystallographica Section C: Structural Chemistry
Publication statusPublished - 2021 Apr 1


  • Debye temperature
  • Ni3Se2
  • NiSe
  • crystal structure
  • nickel selenide
  • single-domain structure

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Physical and Theoretical Chemistry
  • Inorganic Chemistry
  • Materials Chemistry


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