Theoretical prediction and direct observation of the 9<i>R</i> structure in Ag

F. Ernst; M. W. Finnis; D. Hofmann; T. Muschik; U. Schönberger; U. Wolf; M. Methfessel

doi:10.1103/PhysRevLett.69.620

Theoretical prediction and direct observation of the 9R structure in Ag

F. Ernst, M. W. Finnis, D. Hofmann, T. Muschik, U. Schönberger, U. Wolf, and M. Methfessel

Phys. Rev. Lett. 69, 620 – Published 27 July 1992

Abstract

Molecular-dynamics simulations of the Σ3〈110〉(211) twin boundary in Ag predict a thin (1 nm) boundary phase of the 9R (α-Sm) structure. High-resolution electron microscopy shows the presence of the predicted structure. We also calculate the energy ab initio for several hypothetical structures of Cu and Ag. Low energies of the 9R structure and other polytypes, low experimental stacking-fault energies, and the hcp-fcc energy difference are correlated and explained in terms of an effective nearest-neighbor Ising interaction.