title: Superhard nitride-based nanocomposites: role of interfaces and effect of impurities.
abstract: Recently, a hardness similar to that of diamond has been reported for a quasiternary, nitride-based nanocomposite. The related, quasibinary nanocomposite "nc-TiN/a-Si3N4," which may be regarded as the prototype of the family of superhard nc-metal-N/a-Si3N4 systems, also exhibits a significant hardness enhancement. Extensive density-functional theory calculations indicate that the superhardness is related to the preferential formation of TiN(111) polar interfaces with a thin beta-Si3N4-derived layer. The strength of TiN in the 111 direction is similar to that of the weakest bonding direction in diamond. Oxygen impurities cause a significant reduction of the interface strength.
authors.affiliation: School of Physics, The University of Sydney, Sydney NSW 2006, Australia.
authors.forename: Shiqiang
authors.initials: S
authors.lastname: Hao
authors.forename: Bernard
authors.initials: B
authors.lastname: Delley
authors.forename: Stan
authors.initials: S
authors.lastname: Veprek
authors.forename: Catherine
authors.initials: C
authors.lastname: Stampfl