Energy and structure of (001) coincident-site twist boundaries and the free (001) surface in MgO: A theoretical study

Journal Article · Sun Jan 01 00:00:00 EST 1984 · J. Am. Ceram. Soc.; (United States)

DOI:https://doi.org/10.1111/j.1151-2916.1984.tb19137.x· OSTI ID:6231580

Wolf, D

A computer code is described which permits investigation of the energy and structure of coincident-site lattice (CSL) grain boundaries, stacking faults, and free surfaces in ionic crystals. The code uses computational techniques similar to those of Harwell's HADES code for the study of point defects in bulk ionic crystals. Two sets of short-range potentials are used to determine the energy and structure of the free (001) surface and of (001) CSL twist boundaries in MgO with values of ..sigma.., the inverse density of CSL sites, ranging between ..sigma.. = 5 and ..sigma.. = 65. From comparison of the results obtained by means of the different potentials it is concluded that the Van der Waals attraction between oxygen ions on opposite sides of the interface is mainly responsible for the rather weak cohesion predicted for such bicrystals, whereas Coulombic interactions are found to play only a minor role. It then follows that (i) the (001) plane is not a favored plane for the formation of grain boundaries in pure oxides with NaCl structure and (ii) similarities should exist between (001) twist boundaries in ionic crystals with NaCl structure and in fcc metals. These similarities are investigated by comparing calculated boundary structures and energy-vs-misfit angle curves for MgO with recent results for aluminum, copper, silver, and gold, in which a broad spectrum of different interatomic potentials was used. It is suggested that the rather strong cohesion of the pressure-sintered MgO bicrystals of Sun and Balluffi may be due to impurities which have migrated to the boundary during sintering.

• Research Organization: Argonne National Laboratory, Argonne, IL
• OSTI ID: 6231580
• Journal Information: J. Am. Ceram. Soc.; (United States), Vol. 67:1
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
MAGNESIUM OXIDES
FREE ENERGY
GRAIN BOUNDARIES
STACKING FAULTS
COMPUTER CODES
FCC LATTICES
INTERATOMIC FORCES
IONIC CRYSTALS
LATTICE PARAMETERS
SINTERED MATERIALS
SODIUM CHLORIDES
VAN DER WAALS FORCES
ALKALI METAL COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
CHALCOGENIDES
CHLORIDES
CHLORINE COMPOUNDS
CRYSTAL DEFECTS
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CRYSTALS
CUBIC LATTICES
ENERGY
HALIDES
HALOGEN COMPOUNDS
MAGNESIUM COMPOUNDS
MATERIALS
MICROSTRUCTURE
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
SODIUM COMPOUNDS
THERMODYNAMIC PROPERTIES
360202* - Ceramics
Cermets
& Refractories- Structure & Phase Studies