First principles search of hard materials within the SiCN ternary system

Starting from C 3N 4 and Si 3N 4 stoichiometries and from the pseudocubic model structure of the former, intermediate phases SiC 2N 4 and Si 2CN 4 are proposed and geometry optimised within density functional built pseudopotential method using both local density (LDA) and generalised gradient approx...

Full description

Saved in:

Bibliographic Details
Published in:	Solid state sciences Vol. 6; no. 4; pp. 315 - 323
Main Authors:	Betranhandy, Emmanuel, Capou, Lois, Matar, Samir F., El-Kfoury, Charbel
Format:	Journal Article
Language:	English
Published:	Paris Elsevier Masson SAS 2004 Elsevier
Subjects:	ASW Condensed matter: structure, mechanical and thermal properties Crystalline state (including molecular motions in solids) DFT ELF Equations of state of specific substances Equations of state, phase equilibria, and phase transitions Exact sciences and technology GGA Hard materials LDA Physics Structure of solids and liquids; crystallography Structure of specific crystalline solids Theory of crystal structure, crystal symmetry; calculations and modeling Ultra-soft pseudopotentials GGA DFT Ultra-soft pseudopotentials ASW Hard materials LDA ELF Stoichiometry Inorganic compounds Ternary compounds Pseudopotential Ternary systems Binary systems Electronic density of states Equations of state Density functional method Silicon nitrides Generalized gradient approximation Carbon nitrides Semiempirical method Bulk modulus Local density approximation
Online Access:	Get full text
Tags:	Add Tag No Tags, Be the first to tag this record!

Description
Summary:	Starting from C 3N 4 and Si 3N 4 stoichiometries and from the pseudocubic model structure of the former, intermediate phases SiC 2N 4 and Si 2CN 4 are proposed and geometry optimised within density functional built pseudopotential method using both local density (LDA) and generalised gradient approximations (GGA). The ternary compounds are found to be less stable than the two binary systems but the trends in the calculated magnitudes of the bulk moduli B 0 from the fit of the E( V) curves with Birch equation of state: B 0 (SiC 2N 4)=334.5 GPa and B 0 (Si 2CN 4)=270.3 GPa can be interpolated from those of the two extreme compounds: B 0 (C 3N 4)=424.1 GPa and B 0 (Si 3N 4)=219.8 GPa. This translates the chemical role of the substituting element on one hand and allows validating Cohen's semiempirical law relating B 0 to the inverse powers of the average interatomic distances on the other hand. From a mismatch of the chemical bonding in Si(C)NC(Si) chain observed by the electron localisation function (ELF) plot we propose an interpretation for the instability of the intermediate ternary phases. The electronic structure (density of states and band structures) obtained from augmented spherical wave (ASW) calculations of the relaxed structures point to semiconducting behaviour with smaller band gaps for the intermediate phases (∼2 eV, compared with the ∼4 eV gap of binaries). Graphic
Bibliography:	ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23
ISSN:	1293-2558 1873-3085
DOI:	10.1016/j.solidstatesciences.2004.01.010