Atomistic simulation of ideal shear strength, point defects, and screw dislocations in bcc transition metals: Mo as a prototype
- Lawrence Livermore National Laboratory, University of California, Livermore, California 94551 (United States)
Using multi-ion interatomic potentials derived from first-principles generalized pseudopotential theory, we have studied ideal shear strength, point defects, and screw dislocations in the prototype bcc transition metal molybdenum (Mo). Many-body angular forces, which are important to the structural and mechanical properties of such central transition metals with partially filled {ital d} bands, are accounted for in the present theory through explicit three- and four-ion potentials. For the ideal shear strength of Mo, our computed results agree well with those predicted by full electronic-structure calculations. For point defects in Mo, our calculated vacancy-formation and activation energies are in excellent agreement with experimental results. The energetics of six self-interstitial configurations have also been investigated. The {l_angle}110{r_angle} split dumbbell interstitial is found to have the lowest formation energy, in agreement with the configuration found by x-ray diffuse scattering measurements. In ascending order, the sequence of energetically stable interstitials is predicted to be {l_angle}110{r_angle} split dumbbell, crowdion, {l_angle}111{r_angle} split dumbbell, tetrahedral site, {l_angle}001{r_angle} split dumbbell, and octahedral site. In addition, the migration paths for the {l_angle}110{r_angle} dumbbell self-interstitial have been studied. The migration energies are found to be 3{endash}15 times higher than previous theoretical estimates obtained using simple radial-force Finnis-Sinclair potentials. Finally, the atomic structure and energetics of {l_angle}111{r_angle} screw dislocations in Mo have been investigated. We have found that the so-called {open_quote}{open_quote}easy{close_quote}{close_quote} core configuration has a lower formation energy than the {open_quote}{open_quote}hard{close_quote}{close_quote} one, consistent with previous theoretical studies. (Abstract Truncated)
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 383164
- Journal Information:
- Physical Review, B: Condensed Matter, Vol. 54, Issue 10; Other Information: PBD: Sep 1996
- Country of Publication:
- United States
- Language:
- English
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