Mechanically induced stiffening, thermally driven softening, and brittle nature of SiC

Dinesh Varshney,Sanjay Jain,R Khenata,Swarna Shriya,Meenu Varshney

doi:10.1007/s40145-015-0166-9

Abstract

An effective interionic potential calculation with long range Coulomb, charge transfer interaction, covalency effect, short range overlap repulsion extended, van der Waals interaction, and zero point energy effect is implemented to investigate the pressure dependent structural phase transition (ZnS-type (B3) to NaCl-type (B1) structure), and mechanical, elastic, and thermodynamic properties of silicon carbide (SiC). Both charge transfer interaction and covalency effect are important in revealing the pressure induced structural stability, Cauchy discrepancy, anisotropy factor, melting temperature, shear modulus, Young’s modulus, and Gruneisen parameter. We also present the results for the temperature dependent behaviors of normalized volume, hardness, heat capacity, and thermal expansion coefficient. SiC is mechanically stiffened and thermally softened as inferred from pressure (temperature) dependent elastic constant’s behavior. The Pugh’s ratio ∅ = BT / GH, the Poisson’s ratio v, and the Cauchy’s pressure C12–C44 for SiC ceramic confirm its brittle nature.

Highlights

The IV–IV silicon carbide (SiC) possesses tetrahedral C and Si atoms with strong bonds in the lattice
The result on the high pressure elastic constant illustrates that the zinc blende (ZB) structure SiC is unstable when the applied pressure is larger than 126.6 GPa, consistent with the earlier experimental data [3,4] and the molecular dynamics simulation results [13]
At T = 0 K, the thermodynamically stable phase at pressure P is the one with the lowest enthalpy, and the zero temperature theory results in consistent agreement with experiment

Summary

Introduction

The IV–IV silicon carbide (SiC) possesses tetrahedral C and Si atoms with strong bonds in the lattice. The ab initio density functional calculation with the local density approximation (LDA) retraces the transition from zinc blende to rock salt at around 60 GPa [4,5,6,7]. The constant pressure molecular dynamics (MD) simulation for SiC shows the reversible phase transformation from 3C to rock salt [13]. This demonstrates the structural transformation from a four-fold coordinated structure to a six-fold coordinated structure under pressure. The result on the high pressure elastic constant illustrates that the ZB structure SiC is unstable when the applied pressure is larger than 126.6 GPa, consistent with the earlier experimental data [3,4] and the molecular dynamics simulation results [13].

Details of calculations

Results and discussion

B1 discripancy

Conclusions