Fundamental theory of crystal decomposition
Abstract
Lattice defects in or on crystalline materials, determine many technologically important properties. Reliable computerized simulation of such defects are of potential value, and may be expected to contribute to a fundamental understanding of the physical processes that determine the structure and properties of these materials. In the case of point defects, it is attractive to use quantum mechanics to describe the region of the crystal in proximity to the defect, perhaps embedding this region in an external potential determined by some auxiliary principle. The hope here is that the structural response of the lattice to the point defect may then be described by some method which is simpler than the quantum mechanical method used to describe the point defect itself. In the present case, the development is begun for the case of nonmetals. In many studies performed prior to the present for such systems, the use of a classical shell model, based upon point charges, and masses, interacting by simple parameterized potentials has been successful in correlating perfect lattice equilibrium data with the ground state properties of defects in these systems. Therefore, the study was begun by choosing to think of the embedding lattice in terms of the classical shell model. It was found that it is possible to retain the functional form of the shell model, but determine all needed parameters from the quantum mechanical calculation, and to augment this functional form with appropriate angular potentials as well.
 Publication:

Final Report No. 2
 Pub Date:
 May 1991
 Bibcode:
 1991mtu..rept.....K
 Keywords:

 Crystal Lattices;
 Crystals;
 Decomposition;
 Many Body Problem;
 Point Defects;
 Solid State;
 Computerized Simulation;
 Ground State;
 Hartree Approximation;
 Models;
 Quantum Mechanics;
 Quantum Theory;
 Shell Theory;
 SolidState Physics