期刊
PHYSICAL REVIEW B
卷 79, 期 24, 页码 -出版社
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevB.79.245426
关键词
ab initio calculations; density functional theory; electronic structure; hardness; monolayers; nanocomposites; sandwich structures; shear strength; slabs; sodium compounds; titanium compounds
资金
- German Research Foundation (DFG)
- European Commission [5157032]
- Department of Mechanical Engineering
Electronic structure of interfaces, their stability and the mechanism of decohesion in tension as well as of ideal shear have been studied by means of ab initio density-functional theory for heterostructures consisting of a few nanometer thick fcc(NaCl)-TiN slabs with one monolayer of pseudomorphic SiN interface. It is found that the SiN interface sandwiched between fcc(001)-TiN slabs is unstable in its symmetric fcc structure, but it stabilizes by distortion of the Si-N bonds, which lowers the symmetry. Significant strengthening of the SiN interface occurs due to partial transfer of valence charge to the Si containing interface which induces damped valence charge-density oscillations propagating into the TiN bulk. As a consequence of these oscillations, decohesion, and ideal shear does not occur within the SiN interface, but in the TiN slabs between the Ti-N planes parallel to that interface. We provide a detailed study of this mechanism of decohesion and ideal shear on the atomic scale. The results are discussed in the context of the experimentally found hardness enhancement in heterostructures and superhard nanocomposites.
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