Investigating the effect of particle size on Volume-per-atom parameter of TiO2 nanoparticles

Subject Areas : journal of New Materials

علی Mashreghi ¹ (استادیار مهندسی و علم مواد، دانشگاه صنعتی شیراز.)

Received: 2016-06-16 Accepted : 2018-01-29 Published : 2017-11-22

Keywords: TiO2 nanoparticle, Molecular dynamics simulation, Volume-per-atom,

Abstract :

Nanoparticles are considered as one of the most important building blocks of nanotechnology. Due to the high surface to bulk ratio of nanoparticles, most of their properties and parameters differ significantly from their bulk counter parts. One of these parameters is volume of nanoparticle. In the present work, molecular dynamics (MD) simulation was used to explore the effect of amorphous surface layer on volume-per-atom (Ω) of TiO₂ nanoparticles. Two most common phases of TiO₂, rutile and anatase, were investigated. A novel method was proposed for studying the radial variation of Ω from the center to the surface of nanopaticles. It was found that for atoms located in the crystalline core of TiO₂ nanoparticles, the value of Ω is radial independent and is the same as that of bulk TiO₂. However, in the amorphous surface layer, Ω showed radial variation, with its average value larger than that of crystalline core. Moreover, it was observed that the average volume-per-atom (Ω_ave) of TiO₂ nanoparticles is larger that that of bulk TiO₂. For a more detailed examination, the radial variation of coordination number (CN) of titanium ion, from the center to the surface of nanoparticle, was calculated. It was concluded that the lower CN of titanium ions located in the amorphous surface layer, than that of conventional value, i.e. 6, is responsible for larger Ω_ave of TiO₂ nanoparticles.

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