Letter abstract


Nature Materials 6, 44 - 47 (2007)
Published online: 3 December 2006 | doi:10.1038/nmat1795

Hydrogen multicentre bonds

Anderson Janotti & Chris G. Van de Walle

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The concept of a chemical bond stands out as a major development in the process of understanding how atoms are held together in molecules and solids. Lewis' classical picture of chemical bonds as shared-electron pairs1 evolved to the quantum-mechanical valence-bond and molecular-orbital theories2, 3, and the classification of molecules and solids in terms of their bonding type: covalent, ionic, van der Waals and metallic. Along with the more complex hydrogen bonds4 and three-centre bonds5, 6, they form a paradigm within which the structure of almost all molecules and solids can be understood. Here, we present evidence for hydrogen multicentre bonds—a generalization of three-centre bonds—in which a hydrogen atom equally bonds to four or more other atoms. When substituting for oxygen in metal oxides, hydrogen bonds equally to all the surrounding metal atoms, becoming fourfold coordinated in ZnO, and sixfold coordinated in MgO. These multicentre bonds are remarkably strong despite their large hydrogen–metal distances. The calculated local vibration mode frequency in MgO agrees with infrared spectroscopy measurements7. Multicoordinated hydrogen also explains the dependence of electrical conductivity on oxygen partial pressure, resolving a long-standing controversy on the role of point defects in unintentional n-type conductivity of ZnO (refs 8–10).

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  1. Materials Department, University of California, Santa Barbara, California 93106-5050, USA

Correspondence to: Anderson Janotti e-mail: ajanotti@mrl.ucsb.edu

Correspondence to: Chris G. Van de Walle e-mail: vandewalle@mrl.ucsb.edu

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