Better understanding metallic surfaces
Chirality refers to a lack of symmetry. A molecule is chiral if it exists in two states, one being the mirror image of the other, but the mirror image cannot be superimposed on the original molecule. Chiral and achiral metallic surfaces show tremendous potential for use in separation processes, in particular for isolating the more desired of the two forms of a chiral molecule. The majority of research to date regarding chirality of surfaces has been focused on chemical properties, in part due to its relevance to the pharmaceutical industry. However, chirality plays an important role in ‘spintronics’, an emerging field that uses the spin of an electron for the storing, processing and transferring of information. The ‘Stress and magnetism in chiral surfaces’ (Chiramag) project was developed to evaluate the physical properties of chiral surfaces (those that do not exhibit mirror symmetry). Specifically, the researchers have chosen to investigate how the lack of symmetry of a chiral surface is transferred to its physical properties with a focus on surface stress and magnetism. Researchers applied density functional theory (DFT) methods to evaluate the electronic structure of surfaces. Activities to date include analysis of intrinsic surface stress with a focus on relation to electronic structure, development of software to generate surface geometries using exact analytical methods, and analysis of surface states and magnetic structure of metallic surfaces. The investigators determined that surface stress is more highly dependent on the atomic species present (i.e. the specific metallic element) rather than on detailed surface structure. In addition, they have characterised the degree of symmetry breaking produced by adsorption of a chiral compound on an achiral substrate. Finally, the team experimented with and characterised certain metal alloys for use as metal substrates or surfaces. The physical characterisations of metallic chiral and achiral surfaces should play a significant role in the development of so-called spintronic devices. Potential applications for the results include sensors and data storage.