Quantum-Chemical Study of the Structure and Properties of Hypothetical Superhard Materials Based on the Cubic Silicon−Carbon Nitrides

Abstract

Density functional B3LYP/6-31G(d,p) calculations have been carried out to study the structural peculiarities and physical properties of the series of cubic (defect zinc-blende) silicon-carbon nitrides with composition Si x C 3-x N 4 (x ) 0, 1, 2, 3). As model systems, we have considered six clusters with the structure of the adamantane molecule (CH) 4 (CH 2 ) 6 (I), hexamethylenetetramine-like molecules N 4 (CH 2 ) 6-n (SiH 2 ) n (II-V) (n ) 0, 2, 4, 6), and silicon-substituted adamantane molecule (SiH) 4 (SiH 2 ) 6 (VI). These 10 heavy-atom clusters have been used to simulate the crystalline fragments of diamond (I), cubic (defect zinc-blende) siliconcarbon nitrides (II-V), and cubic (zinc-blende) silicon solid (VI). It was found that the full B3LYP/6-31G(d,p) geometry optimization of these clusters allow us to reproduce the structures, unit cell parameters, and bulk modulus (hardness) of real crystals (I and VI) quite well and to predict the structural and mechanical properties of the hypothetical crystalline compounds (II-V).

Adsorption, Isomerization, and Decomposition of HCN on Si(100)2 × 1: A Computational Study with a Double-Dimer Cluster Model

“…The interaction of CN-containing species with Si surfaces is practically relevant to the chemical vapor deposition (CVD) of SiCN x films which have been shown to exhibit crystalline texture. − The mechanism for the adsorption and reactions of CN-containing compounds (such as HCN and C 2 N 2 ) with the single crystal surfaces of Si has been investigated recently in this laboratory to understand the chemistry of CN x −Si interactions. − …”

“…The interaction of CN-containing species with Si surfaces is practically relevant to the chemical vapor deposition (CVD) of SiCN x films which have been shown to exhibit crystalline texture. [1][2][3] The mechanism for the adsorption and reactions of CN-containing compounds (such as HCN and C 2 N 2 ) with the single crystal surfaces of Si has been investigated recently in this laboratory to understand the chemistry of CN x -Si interactions. [4][5][6] Bu et al 4 reported the adsorption and thermal reaction of HCN (DCN) on Si(100)-2 × 1 using ultraviolet photoelectron spectroscopy (UPS), X-ray photoelectron spectroscopy (XPS), and high-resolution electron energy loss spectroscopy (HREELS).…”

Growth, Characterization, and Properties of Carbon Nitride With and Without Silicon Addition

“…n C n N 4 (n=0, 1, 2, 3) indicate that as more C atoms are substituted for Si atoms in Si 3 N 4 (i.e., an increase of the number n), the bulk modulus is progressively increased. [33,34] Since many properties, hardness included, depend more on short-range order than on long-range order, a-SiCN materials that contain similar chemical bonding and atomic local order of Si, C and N to those in crystalline counterparts would exhibit properties comparable to c-SiCN. However, in most amorphous phases, all possible C hybridization configurations (sp 1 , sp 2 and sp 3 ) are likely to be present.…”