First principles search of hard materials within the SiCN ternary system

摘要: Abstract Starting from C3N4 and Si3N4 stoichiometries the pseudocubic model structure of former, intermediate phases SiC2N4 Si2CN4 are proposed geometry optimised within density functional built pseudopotential method using both local (LDA) generalised gradient approximations (GGA). The ternary compounds found to be less stable than two binary systems but trends in calculated magnitudes bulk moduli B0 fit E(V) curves with Birch equation state: (SiC2N4)=334.5 GPa (Si2CN4)=270.3 GPa can interpolated those extreme compounds: (C3N4)=424.1 GPa (Si3N4)=219.8 GPa. This translates chemical role substituting element on one hand allows validating Cohen's semiempirical law relating inverse powers average interatomic distances other hand. From a mismatch bonding Si(C)NC(Si) chain observed by electron localisation function (ELF) plot we propose an interpretation for instability phases. electronic (density states band structures) obtained augmented spherical wave (ASW) calculations relaxed structures point semiconducting behaviour smaller gaps (∼2 eV, compared ∼4 eV gap binaries).