Indian Journal of Physics

, Volume 83, Issue 1, pp 31–47 | Cite as

How does contrasting dependence of impurity-atom diffusivity on the density of host disordered medium arise?

  • Manju Sharma
  • S. YashonathEmail author


We report results of molecular dynamics investigations into neutral impurity diffusing within an amorphous solid as a function of the size of the diffusant and density of the host amorphous matrix. We find that self diffusivity exhibits an anomalous maximum as a function of the size of the impurity species. An analysis of properties of the impurity atom with maximum diffusivity shows that it is associated with lower mean square force, reduced backscattering of velocity autocorrelation function, near-exponential decay of the intermediate scattering function (as compared to stretched-exponential decay for other sizes of the impurity species) and lower activation energy. These results demonstrate the existence of size-dependent diffusivity maximum in disordered solids. Further, we show that the diffusivity maximum is observed at lower impurity diameters with increase in density. This is explained in terms of the Levitation parameter and the void structure of the amorphous solid. We demonstrate that these results imply contrasting dependence of self diffusivity (D) on the density of the amorphous matrix, ρ. D increases with ρ for small sizes of the impurity but shows an increase followed by a decrease for intermediate sizes of the impurity atom. For large sizes of the impurity atom, D decreases with increase in ρ. These contrasting dependence arises naturally from the existence of Levitation Effect.


Amorphous solid anomalous diffusion density impurity 


61.43.-j 66.30.hh 66.30.Ny 


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  1. [1]
    Y Zhou and G H Miller Physical Review E53 1587 (1996)ADSGoogle Scholar
  2. [2]
    S Yashonath and P K Ghorai J. Phys. Chem. B112 665 (2008)Google Scholar
  3. [3]
    D Kivelson, S K Jensen and M-K Ahn J. Chem. Phys. 58 428 (1973)CrossRefADSGoogle Scholar
  4. [4]
    B Alder and W E Alley J. Chem. Phys. 61 1415 (1974)CrossRefADSGoogle Scholar
  5. [5]
    G Tarjus and D Kivelson J. Chem. Phys. 103 3071 (1995)CrossRefADSGoogle Scholar
  6. [6]
    Y Jung, J P Garrahan and D Chandler Physical Review E69 061205 (2004)Google Scholar
  7. [7]
    A Pradel, T Pagnier and M Ribes Solid State Iomics 17 147 (1985)CrossRefGoogle Scholar
  8. [8]
    M Hosono, J Kawamura, H Itoigawa, N Kuwata, T Kamiyama and Y Nakamura J. of Non-Crystalline Solids 244 81 (1999)CrossRefADSGoogle Scholar
  9. [9]
    T Minami J. of Non-Crystalline Solids 73 273 (1985)CrossRefADSGoogle Scholar
  10. [10]
    L V Woodcock, C A Angell and P Cheeseman J. Chem. Phys. 65 1565 (1976)CrossRefADSGoogle Scholar
  11. [11]
    C A Angell, P A Cheeseman and S Tamaddon Science 218 885 (1982)CrossRefADSGoogle Scholar
  12. [12]
    P K Ghorai and S Yashonath J. Phys. Chem. B109 5824 (2005)Google Scholar
  13. [13]
    M Sharma and S Yashonath J. Phys. Chem. B110 17217 (2006)Google Scholar
  14. [14]
    M Parrinello, A Rahman and P Vashishtha Phys. Rev. Lett. 50 1073 (1983)CrossRefADSGoogle Scholar
  15. [15]
    P Vashishtha and A Rahman Phys. Rev. Lett. 40 1337 (1978)CrossRefADSGoogle Scholar
  16. [16]
    The dl-poly-2.13. W Smith and T Forester CCLRC, Daresbury Laboratory, Daresbury (2001)Google Scholar
  17. [17]
    S Yashonath and P Santikary J. Phys. Chem. 98 6368 (1994)CrossRefGoogle Scholar
  18. [18]
    S Yashonath and V C Bhasu J. Chem. Phys. Lett. 189 311 (1992)CrossRefADSGoogle Scholar
  19. [19]
    T Yoshidome, A Yoshimori and T Odagaki Phys. Rev. E76 021506 (2007)Google Scholar

Copyright information

© Indian Association for the Cultivation of Science 2009

Authors and Affiliations

  1. 1.Solid Sate and Structural Chemistry UnitIndian Institute of ScienceBangaloreIndia

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