A Bond-Order Potential Incorporating Analytic Screening Functions for the Molybdenum Silicides

Abstract

The intermetallic compound MoSi2, which adopts the C11b crystal structure, and related alloys exhibit an excellent corrosion resistance at high temperatures but tend to be brittle at room and even relatively high temperatures. The limited ductility of MoSi2 in ambient conditions along with the anomalous temperature dependence of the critical resolved shear stress (CRSS) of the {110)<111], {011)<100] and {010)<100] slip systems and departure from Schmid law behavior of the {013)<331] slip system can all be attributed to complex dislocation core structures. We have therefore developed a Bond-Order Potential (BOP) for MoSi2 for use in the atomistic simulation of dislocations and other extended defects. BOPs are a real-space, O(N), two-center orthogonal tight-binding formalism that are naturally able to describe systems with mixed metallic and covalent bonding. In this development novel analytic screening functions have been adopted to properly describe the environmental dependence of bond integrals in the open, bcc-based C11b crystal structure. A many-body repulsive term is included in the model that allows us to fit the elastic constants and negative Cauchy pressures of MoSi2. Due to the internal degree of freedom in the position of the Si atoms in the C11b structure which is a function of volume, it was necessary to adopt a self-consistent procedure in the fitting of the BOP. The constructed BOP is found to be an excellent description of cohesion in C11b MoSi2 and we have carefully assessed its transferability to other crystal structures and stoichiometries, notably C40, C49 and C54 MoSi2, A15 and D03 Mo3Si and D8m Mo5Si3 by comparing with ab initio structural optimizations.

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References

  1. 1.

    M. Yamaguchi, H. Inui and K. Ito, Acta Mater. 48, 307 (2000)

    CAS  Article  Google Scholar 

  2. 2.

    K. Ito, H. Inui, Y. Shirai and M. Yamaguchi, Phil. Mag. A 72, 1075 (1995)

    CAS  Article  Google Scholar 

  3. 3.

    M. S. Daw and M. I. Baskes, Phys. Rev. B 29, 6443 (1984)

    CAS  Article  Google Scholar 

  4. 4.

    M. W. Finnis and J. E. Sinclair, Phil. Mag. A 50, 45 (1984)

    CAS  Article  Google Scholar 

  5. 5.

    A. P. Horsfield, A. M. Bratkovsky, M. Fearn, D. G. Pettifor and M. Aoki, Phys. Rev. B 53, 12694 (1996)

    CAS  Article  Google Scholar 

  6. 6.

    D. Nguyen-Manh, D. G. Pettifor, D. J. H. Cockayne, M. Mrovec, S. Znam and V. Vitek, Bull. Mater. Sci. 26, 43 (2003)

    CAS  Article  Google Scholar 

  7. 7.

    M. Mrovec, D. Nguyen-Manh, D. G. Pettifor and V. Vitek, Phys. Rev. B 69, 094115 (2004)

    Article  Google Scholar 

  8. 8.

    M. J. Cawkwell, D. Nguyen-Manh, V. Vitek and D. G. Pettifor, Mat. Res. Soc. Symp. Proc. Vol. 779, W5.5.1 (2003)

    Article  Google Scholar 

  9. 9.

    S. Znam, D. Nguyen-Manh, D. G. Pettifor and V. Vitek, Phil. Mag. 83, 415 (2003)

    CAS  Article  Google Scholar 

  10. 10.

    D. Nguyen-Manh, D. G. Pettifor, S. Znam and V. Vitek, Mat. Res. Soc. Symp. Proc. Vol. 491, 353 (1998)

    CAS  Article  Google Scholar 

  11. 11.

    D. Nguyen-Manh, D. G. Pettifor and V. Vitek, Phys. Rev. Lett. 85, 4136 (2000)

    CAS  Article  Google Scholar 

  12. 12.

    P. Blaha, K. Schwarz, G. K. H. Madsen, D. Kvasnicka and J. Luitz, WIEN2k, An Augmented Plane Wave + Local Orbitals Program for Calculating Crystal Properties, (Karlheinz Schwarz, Techn. Universität Wien, Austria), 2001. ISBN 3–9501031–1–2

    Google Scholar 

  13. 13.

    A. P. Sutton, M. W. Finnis, D. G. Pettifor and Y. Ohta, J. Phys. C: Solid State Phys. 21, 35 (1988)

    Article  Google Scholar 

  14. 14.

    F. Ducastelle and F. Cyrot-Lackmann, J. Phys. Chem. Sol. 31, 1295 (1970)

    CAS  Article  Google Scholar 

  15. 15.

    C. Lanczos, J. Res. Nat. Bur. Stand. 45, 255 (1950)

    Article  Google Scholar 

  16. 16.

    K. Tanaka, K. Nawata, H. Inui, M. Yamaguchi and M. Koiwa, Intermetallics 9, 603 (2001)

    CAS  Article  Google Scholar 

  17. 17.

    K. Tanaka, H. Onome, H. Inui, M. Yamaguchi and M. Koiwa, Mat. Sci. Eng. A 239–240, 188 (1997)

    Article  Google Scholar 

Download references

Acknowledgements

This research was supported by the U.S. Department of Energy, BES Grant no. DE-PG02-98ER45702 (M.J.C. and V.V.) and the United Kingdom EPSRC (D.N.M. and D.G.P.).

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Correspondence to Marc J. Cawkwell.

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Cawkwell, M.J., Mrovec, M., Nguyen-Manh, D. et al. A Bond-Order Potential Incorporating Analytic Screening Functions for the Molybdenum Silicides. MRS Online Proceedings Library 842, 126–131 (2004). https://doi.org/10.1557/PROC-842-S2.8

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