On the thermodynamic stability of amorphous intergranular films in covalent materials

Journal Article · Sat Mar 01 04:00:00 EST 1997 · Journal of the American Ceramic Society

DOI:https://doi.org/10.1111/j.1151-2916.1997.tb02889.x· OSTI ID:474153

Keblinski, P; Phillpot, S R; Wolf, D ^[1]; Gleiter, H ^[2]

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1. Argonne National Lab., IL (United States). Materials Science Div.
2. Forschungszentrum Karlsruhe (Germany)

The thermodynamic origin, structure, and stability of the thin amorphous films commonly found in grain boundaries in covalent ceramics are investigated by molecular-dynamics simulation. to focus on the purely thermodynamic aspects, any kinetic effects associated with impurity-controlled interface chemistry are excluded by investigating pure silicon (described by the Stillinger-Weber three-body potential). For this single-component covalent model material, the authors demonstrate that all high-energy boundaries exhibit a universal amorphous structure, with a width of {approximately}0.25 nm, whereas low-energy boundaries are crystalline and much sharper. They also demonstrate that introduction of an amorphous film into a crystalline interface lowers the excess energy to a level similar to the energy of two bulk crystal-amorphous interfaces. The competition between a narrow crystalline boundary structure and a wider amorphous boundary structure is shown to be governed by the relative excess energies of the atoms in the grain boundaries and in the bulk amorphous phase. These observations suggest that, in principle, amorphous grain-boundary films do not require impurities for their stabilization and that, as first proposed by Clarke, an equilibrium grain-boundary phase of uniform thickness can be the result of purely thermodynamic rather than kinetic factors.

• Research Organization: Argonne National Laboratory (ANL), Argonne, IL
• Sponsoring Organization: Deutsche Forschungsgemeinschaft, Bonn (Germany); USDOE, Washington, DC (United States)
• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 474153
• Journal Information: Journal of the American Ceramic Society, Journal Name: Journal of the American Ceramic Society Journal Issue: 3 Vol. 80; ISSN 0002-7820; ISSN JACTAW
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
AMORPHOUS STATE
COMPUTERIZED SIMULATION
ENERGY LEVELS
GRAIN BOUNDARIES
INTERFACES
MATHEMATICAL MODELS
SILICON
THERMODYNAMIC PROPERTIES