Theoretical investigation on improving the hardness of novel superhard materials by doping

Abstract

newline The present thesis aims to identify new hard/superhard materials newlineby performing electronic structure calculations on sixteen newlineNitrogen/Boron/Transition Metal doped B(P/As)xN1-x/ AlxB1-xN/ newlineTM10.5TM20.5B2 ternary materials. Ab-initio full potential-linearized newlineaugmented plane wave method (FP-LAPW) using density functional newlinetheory (DFT), interfaced with the Wien2k package is adopted. Using newlinegeneralized gradient approximation as an exchange and correlation newlinefunctional, the structural, electronic, mechanical, optical, thermal and newlinetransport properties of binary III-V semiconductors such as BP, BAs, BN, newlineAlN (216-F4 3m) and transition metal diborides such as ScB2, TiB2, VB2, newlineZrB2 (191-P6/mmm) along with sixteen of their ternary phases newlineBP0.75N0.25, BP0.5N0.5, BP0.25N0.75, BAs0.75N0.25, BAs0.5N0.5, BAs0.25N0.75 newlineB0.125Al0.875N, B0.25Al0.75N, B0.5Al0.5N, B0.75Al0.25N, B0.875Al0.125N, newlineTi0.5Sc0.5B2, Ti0.5V0.5B2, Zr0.5Sc0.5B2, Zr0.5Ti0.5B2, and Zr0.5V0.5B2 are newlinereported in the present thesis. newlineNitrogen addition is done to boron phosphide and boron arsenide. newlineBand structure and density of states study reveal that the parent binary newlinesuch as BP, BAs and BN materials possess indirect band gap whereas newlinethe ternary materials BP0.75N0.25, BP0.5N0.5, BP0.25N0.75, BAs0.75N0.25, newlineBAs0.5N0.5, and BAs0.25N0.75 are turned out to have a direct band gap. The newlinehardness of ternary BP0.25N0.75 and BAs0.25N0.75 materials are computed newlineas 44 GPa and 40 GPa respectively which make these materials to be newlinevii newlinesuperhard materials.