The fracture strength of AlLiB 14 Scott P. Beckman, Iowa State University, DMR 1105641

1. The fracture strength of AlLiB14Scott P. Beckman, Iowa State University, DMR 1105641 Beckman and Wan present a technique to accurately predict the fracture strength of brittle crystalline materials using a small set of ideal brittle cleavage strength calculations and the components of the elastic tensor. Using this method the fracture strength of the AlLiB14 compound is examined. This method allows for insight regarding the local bonding within the crystal. It is concluded that the critical bonds are those that span between the B12 icosahedral substructures. This may allow engineers to develop a strategy to control the mechanical properties of this crystal family. Wan and Beckman “The fracture strength of AlLiB14” in press at Physical Review Letters (2012). This figure shows the charge density the collects between the icosahedra in the XYB14 crystal family. It is these bonds that are critical for controlling the strength of the crystal.

2. The fracture strength of AlLiB14Scott P. Beckman, Iowa State University, DMR 1105641 The development of new superhard materials that can operate under extreme conditions is critical for high-performance industrial manufacturing and is a subject that has recently received great attention. A specimens of crystals in the XYB14 crystal family have been experimentally shown to potentially be superhard. These crystals are open and have low symmetry which makes them unlike most other superhard compounds; however there have been very few fundamental studies aimed an understanding the individual bonding in the crystals. Here for the first time we present a study that allows for insight to the nature of the bonding and the hardness of these crystals. This photograph shows the graduate student Liwen F. Wan explaining her research to Prof. Beckman.