Electronic Bonding Revealed by Electron Diffraction
When atoms come together to form a crystal, a redistribution of electron charge creates bonds that govern almost all of the crystal's physical and chemical properties. Ab initio calculations can provide theoretical determination of the bonding charge density, but experimental verification can be fraught with difficulty because the change in the total charge density, as measured via diffraction experiments, is very small. For example, in aluminum (Al), most of the electrons are highly delocalized and form a free electron gas, but some of the electron density forms highly directional bonds. On page 1583 of this issue, Nakashima et al. ( 1 ) demonstrate the use of ultrasensitive convergent-beam electron diffraction (CBED) to map the bonding charge density of Al to an unrivaled accuracy. These results lead to a greater understanding of this metal's mechanical properties.