Isotope effect in hydrogen/deuterium-absorbing Pd nanoparticles revealed by X-ray powder diffraction and by a multi-component MO method

Takayoshi Ishimoto, Masanori Tachikawa, Miho Yamauchi, Hiroshi Kitagawa, Hiroaki Tokiwa, Umpei Nagashima

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

The isotope effect in Pd nanoparticles that absorb hydrogen or deuterium (i.e., H/D isotope effect) was studied experimentally and theoretically. First, the geometries (i.e., lattice parameters) of such Pd nanoparticles exposed to hydrogen or deuterium gas were measured by using X-ray powder diffraction to determine the lattice parameters. Then, the geometrical and electronic relaxations of PdnH- and PdnD- (n = 1-6) clusters, which modeled Pd nanoparticles exposed to hydrogen or deuterium gas, were calculated by using a multi-component molecular orbital (MC_MO) method, which uses first principles of quantum mechanics to account for the quantum effect of proton/deuteron. Experimental results from the diffraction patterns show that the bond distances of Pd nanoparticles exposed to hydrogen gas (and thus had absorbed hydrogen) were about 0.005 Å longer than those of exposed to deuterium gas. These results were confirmed by analytical results from the MC_MO calculation for PdnH- and Pd nD- clusters. Therefore, the local geometrical changes due to the H/D isotope effect control the geometrical changes of the entire nanoparticle. Both the experimental and analytical results also show that the nanoparticle (cluster) size influences the extent of the H/D isotope effect on the geometrical changes. Based on the analytical results, the electronic charge densities are only slightly influenced by the H/D isotope effect.

Original languageEnglish
Pages (from-to)1775-1780
Number of pages6
Journaljournal of the physical society of japan
Volume73
Issue number7
DOIs
Publication statusPublished - 2004 Jul 1
Externally publishedYes

Keywords

  • Geometrical and electronic relaxations
  • Hydrogen/deuterium-absorbing Pd nanoparticle
  • Isotope effect
  • Multi-component molecular orbital method
  • Quantum effect
  • Size dependency

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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