Electronic and structural origin of ultraincompressibility of 5d transition-metal diborides MB(2) (M=W, Re, Os).
First-principles theory was used to investigate the roles of bond topology and covalency in the phase stability and elastic strength of 5d transition-metal diborides, focusing on elements (M=W, Re, Os) that have among the lowest compressibilities of all metals. Among the phases studied, the ReB(2)-type structure exhibits the largest incompressibility (c axis), comparable to that of diamond. This ReB(2) structure is predicted to be the ground-state phase for WB(2) and a pressure-induced phase (above 2.5 GPa) for OsB(2). Both strong covalency and a zigzag topology of interconnected bonds underlie these ultraincompressibilities. Interestingly, the Vickers hardness of WB(2) is estimated to be similar to that of superhard ReB(2).
Chen
Xing-Qiu
XQ
Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6114, USA.
Fu
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CL
Krcmar
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Painter
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