They found they could make «bulk» metallic glass by using three or more elements that differ from one another in atomic size by at least 12 percent. (discovermagazine.com)
Tafti and his team turned to copper due to its ideal atomic size, which is between lithium and sodium. (sciencedaily.com)
Hydrogen has a very small atomic size (it is the smallest most basic of all the elements) and so can be packed quite tightly even into solids. (earthtimes.org)