Beyond the bonds that bind: UCSB researchers discover
hydrogen can form multicenter bonds
Researchers at the University of California, Santa
Barbara have shown that, under the right circumstances, hydrogen can
form multicenter bonds, where one hydrogen atom simultaneously bonds
to as many as four or six other atoms.
Tested for hydrogen in metal oxides, the discovery
could have a broad range of technological impact. The research is
available in the advance online publication of Nature Materials.
Professor Chris G. Van de Walle and Project Scientist Anderson Janotti,
both of the Materials Department of the College of Engineering at UC
Santa Barbara, have shown that multi-coordinated hydrogen is a likely
explanation for electronic conductivity in metal oxides. Metal oxides
are widely used in everything from sunscreen to sensors.
Hydrogen, the simplest of the elements (consisting of one proton and
one electron) is typically expected to exhibit simple chemistry when
forming molecules or solids. Hydrogen atoms almost always form a
single bond to just one other atom, leading to a two-center bond with
two electrons. Exceptions to the rule are rare; there are only a few
cases when hydrogen bonds simultaneously to two other atoms, forming a
three-center bond.
Hydrogen can replace an oxygen atom and form a multicenter bond with
adjacent metal atoms. For example, in ZnO, hydrogen equally bonds to
the four surrounding Zn atoms, becoming fourfold coordinated. These
multicenter bonds are highly stable and explain previously puzzling
variations in conductivity as a function of temperature and oxygen
pressure. The results suggest that hydrogen can be used as a
substitutional dopant in oxides, a concept that is counterintuitive
and should be of wide interest to researchers.
Source / Further
information:
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Publishing date: 05-Dec-2006
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Anderson Janotti and Chris G. van de Walle -
Hydrogen multicentre bonds - Nature Materials AOP,
doi:10.1038/nmat1795
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