Berlin 2005 – wissenschaftliches Programm
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M: Metallphysik
M 38: Mechanische Eigenschaften I
M 38.3: Vortrag
Dienstag, 8. März 2005, 11:00–11:15, TU H111
An ab initio study of the connection between elasticity and crack formation — •Petr Lazar1, Raimund Podloucky1, and Walter Wolf2 — 1Institute for Physical Chemistry of Univ. Vienna, Liechtensteinstrasse 22A, A 1090 Vienna, Austria — 2Materials Design s.a.r.l., 44, av. F.-A. Bartholdi, 72000 Le Mans, France
The connection between elasticity and crack formation is of long-time interest. The conceptual problem is that the elastic response to an external load is nonlocal because the energy dissipates over the whole material, whereas the crack formation energy is localized around the crack. Our crucial ansatz is, that at a critical load or crack size, elastic response and crack formation are in equilibrium and now the elastic energy is also localized. For single crystals we studied the formation of cracks of type 1 for which the crack is initialized by cleaving the material. The two extreme cases were considered: 1) no atomic relaxation after crack formation (ideal brittle cleavage) [1]; 2) full relaxation in terms of a perfect elastic response. From ab initio calculations [2] for a variety of materials and crack directions we obtain the energy as a function of crack size which serves for the derivation of model parameters. Based on this combination of ab initio data and analytic modelling we arrive at the equation C = a G, in which C is an elastic modulus, G is the cleavage energy, and a is a parameter of local character.
[1] Rose et al., PRB 28,1835 (1983)
[2] G. Kresse and J. Joubert, PRB 59,1758 (1999)
Supported by the Austrian Science Fund (Science College W4).