Dislocation mechanism

Very recently, people who engage in computer simulation of crystals that contain dislocations have begun attempts to bridge the continuum/atomistic divide, now that extremely powerful computers have become available. It is now possible to model a variety of aspects of dislocation mechanics in terms of the atomic structure of the lattice around dislocations, instead of simply treating them as lines with macroscopic properties (Schiotz et al. 1998, Gumbsch 1998). What this amounts to is linking computational methods across different length scales (Bulatov et al. 1996). We will return to this briefly in Chapter 12. 

The comparison of the Re content of a molybdenite with its structural polytype has been proposed as a method for assessing the viability of samples for Re-Os dating. 3R molybdenite has been assumed to grow via a screw dislocation mechanism triggered by the incorporation of Re during crystallisation. Low Re 3R ... 

See Appendix C for a brief survey of mathematical relations for curves and surfaces. 5See standard references on dislocation mechanics [2, 4, 5],... 

J. Weertman. Dislocation mechanics at high strain rates. In R.W. Rohde, B.M. Butcher, J.R. Holland, and C.H. Karnes, editors, Metallurgical Effects at High Strain Rates, pages 319-332, New York, 1973. Plenum Press. 

L.E. Shilkrot et al Multiscale plasticity modeling Coupled atomistics and discrete dislocation mechanics. J. Mech. Phy. Solids 52, 755-787 (2004)... 

D nucleation occurs when nuclei at the crystal surfaces act as sources of steps that allow for the further incorporation of growth units. In general, this mechanism accounts for the crystal growth observed at high supersaturations. The screw dislocation mechanism often accounts for growth at lower supersaturations. When the supersaturation is below the threshold for formation of 2-D nuclei, the presence of screw dislocations provides a source of steps for the addition of growth units in an infinite sequence of equidistant and parallel steps. 

The primary mechanism for seismic anisotropy in the mantle is thought to be due to the lattice preferred orientation (LPO) of olivine and other dominant minerals. Numerical predictions of mantle flow-fields can be used to predict LPO as a result of dislocation mechanisms and hence the seismic anisotropy (e.g. Blackman et al. 1996 ... 

In this chapter we first briefly discuss the techniques of porous SiC substrate preparation and some of the relevant properties of the substrates. Following that, we describe the results from our GaN films on the porous SiC substrates, including details of both dislocation mechanisms and strain evolution in the films. 

Dislocation Mechanisms in GaN Films Grown on Porous Substrates or Interlayers... 

A major focus in the study of mixed metal ion systems has been to examine metal ion discrimination. In particular, two specific mechanisms can be attributed to metal ion discrimination macrocyclic hole size and what Lindoy has termed as a dislocation mechanism. The key to this... 

---