From detailed assessments of electronic structure, researchers at the University at Buffalo, Cornell University, Stony Brook University and Moscow State University discovered that unexpected hydrides violating standard valence rules, such as LiH 6 and LiH 8 , become stable metals at a pressure approximately one quarter of that required to metalize pure hydrogen itself; findings that were published in an October 5, 2009 early edition of the Proceedings of the National Academy of Sciences.
Some hydrides become stable metals under pressure