The refractory transition metal—carbides commonly fail under stress by brittle fracture and the properties and nature of the fracture process are consequently of practical interest. We have calculated the fracture properties of titanium carbide under tensile stress using our full—potential LMTO method, a methodology which is closely related to multiple scattering theory (and includes a true interstitial region). The fracture calculation is accomplished by employing a repeated slab (or repeated cleavage separation) geometry. Within this geometry, the fracture process is simulated most simply by uniformly increasing the gap separation from zero to a distance on the order of a few atomic radii. A more sophisticated search for fracture instability involved stretching the ideal crystal and examining the separation energetics of the strained system.

Results of these calculations will be reported both for the ideal, stoichiometric titanium carbide crystal and also for systems containing carbon vacancies. We will discuss therole of such defects in modifying the bonding behavior at the cleavage plane and the resulting effect on resistance to fracture.