Site preference activation energy

1. Properties of solute atoms in intermetallic compoundsGary S. Collins, Washington State University, DMR 0904096 PAC, a nuclear hyperfine method, was used to measure lattice locations and jump frequencies of impurity solute atoms in equilibrium at high temperature. The study was on compounds of rare-earth elements and palladium. Crystal structure of RPd3 phases. R atoms at corners, Pd atoms at face centers. It was found that: (1) Indium solutes prefer rare-earth sites in Ce-, Pr- and NdPd3 phases, but palladium sites in Sm and EuPd3 phases. The top figure shows a systematic increase and change in sign of the site-preference energy along the series. (2) Jump frequencies of In solutes are very high for CePd3 and decrease along the series. The bottomfigure shows that jump-frequency activation energies increase linearly along the series. Both properties are correlated with the vacancy concentration on Pd-sublattice, which is concluded from the measurements to be greater at the Ce end of the series. In in RPd3 Site preference activation energy In in RPd3 Diffusional jump activation energy

2. Properties of solute atoms in intermetallic compoundsGary S. Collins, Washington State University, DMR 0904096 This is the first study correlating trends in site preferences and jump frequencies in a series of compounds. A broader impact is observation and interpretation of a correlation between these two properties of solute atoms that are not otherwise related in an obvious way. The study was carried out by Qiaoming Wang (MS, May 2012). Qiaoming presented a poster at WSU in March comparing site preferences of solute atoms in these RPd3 compounds and RAl2 compounds. A paper will be presented orally by Collinsin plenary session in September at the International Conference on Hyperfine Interactions, Beijing, and will subsequently appear in the journal Hyperfine Interactions. Group photo May 2012: from left, Randy Newhouse (PhD 2012), Qiaoming Wang (MS 2012) and Matt Zacate, Associate Professor at Northern Kentucky University. Qiaoming carried out the present research. Randy, PhD 2012, studied diffusion in other phases. Matt is a long-standing collaborator who helps us interpret dynamically relaxed PAC signals.