Comparative first-principles molecular dynamics study of TiN(001)/SiN/TiN(001) and TiN(001)/SiC/TiN(001) interfaces in superhard nanocomposites

Abstract

Heterostructures TiN(001)/SiN/TiN(001) and TiN(001)/SiC/TiN(001), with one monolayer (ML) of interfacial SiN and SiC, respectively, inserted between five monolayer thick B1-TiN, were investigated using first-principles quantum molecular dynamics (QMD) calculations. The temperature dependent QMD simulations at 300 K in combination with subsequent variable-cell structural relaxation revealed that the TiN(001)/SiN/TiN(001) interface exists as pseudomorphic B1-SiN layer only at 0 K, and as a superposition of distorted octahedral SiN6 and tetrahedral SiN₄ units aligned along the (110) direction at a finite temperature. Thus, at 300 K, the interfacial layer is not epitaxial. Instead it consists of aggregates of the B1-SiN-like and Si₃N₄-like distorted clusters. However, in the the TiN(001)/SiC/TiN(001) heterostructures, the interfacial layer remains epitaxial B1-SiC at 0 K as well as at 300 K, with only a small shift of nitrogen atoms on both sides of the interface towards the silicon atoms. A comparison with the results obtained by earlier "static" ab initio DFT calculations at 0 K shows the great advantage of the QMD calculations that allow us to reveal structural reconstructions caused by thermal activation. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/20546