Interface Formation and Percusory Dynamics
Abstract
A completely ab-initio investigation of grain boundaries in solids has been performed for the first time. The electronic and structural properties of two short-period twist boundaries in Ge have been explored and found to be extremely complex. Boundary bonds are found to be distorted and weak, three-fold and five-fold coordinated defects appear to exist, and topological disorder in the form of odd and even numbers of rings of bonds is found to prevail. Complete total energy surfaces as a function of displacement of one grain over the other have also been mapped out. The results predict that there is a large degeneracy in the number of local energy minima, that tunneling-like modes should exist in these boundaries, that the formation energies of the boundaries lie in the range between 4 and 7 eV per unit cell, that the boundary volumes involve expansions in the range of 0.1 to 0.3 A/unit area, that trends toward dimerization exist parallel to the boundary planes, that electronic states will exist deep in the fundamental gaps of these systems.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 09, 1990
- Accession Number
- ADA224128
Entities
People
- John D. Joannopoulos
Organizations
- Massachusetts Institute of Technology