Evaluation of Spinodal Pressure for Gallium nitride in the Zinc-blend and Wurtzite Structures by Using Different Equations of State (EOSs)

Salar A Mawlood,Mumtaz M Hussien,Adnan M Al-Sheikh

doi:10.33899/rjs.2018.143957

Abstract

According to the definition of spinodal pressure as the negative pressure at which bulk modulus (of a substance) go to zero. Extrapolation of variation of bulk modulus results with pressure has been used to evaluate spinodal pressure for GaN in zinc-blende and wurtzite structures using different equations of state (EOS) (Birch-Murnaghan, Bardeen, Libby and Libby, and Born-Mie). Result obtained in the present work for GaN in the zinc-blende structure using Born-Mie equation of state shows a good agreement with literature. While results for wurtzite structure, obtained by using Birch-Murnaghan and Bardeen EOSs are in a good agreement with literature. Present results and many literature show that (Jiuxun, 2005) approach for evaluation of spinodal pressure yield results in less agreement with other works

Highlights

Result obtained in the present work for GaN in the zinc-blende structure using Born-Mie‬‬ ‫‪equation of state shows a good agreement with literature
Experimental results are meager and quite hard to obtain in the neighborhood of spinodal limit, because spinodal is the limit of metastability of substance with respect to phase transition, we used extrapolation of bulk modulus data under high pressure shown in Fig. (1) and Fig. (2), combining these data with equation 5, and the definition of spinodal pressure as the negative pressure at which bulk modulus value go to zero
The spinodal pressure values for GaN obtained in present work is close together with results obtained from works of (Cheng et al, 2008), and (Gupta and Rana, 2012), but differ from that obtained by (Jiuxun, 2005), this may be attributed to the fact that our present work used first principle approach in evaluation of Psp for material obtained within the metastable state, while work didn’t consider that (Psp) for the material obtained within the metastable state

Summary

Introduction

Extrapolation of variation of bulk modulus results with‬‬ ‫‪pressure has been used to evaluate spinodal pressure for GaN in zinc-blende and wurtzite structures‬‬ ‫‪using different equations of state (EOS) (Birch-Murnaghan, Bardeen, Libby and Libby, and Born‬‬‫‪Mie). Result obtained in the present work for GaN in the zinc-blende structure using Born-Mie‬‬ ‫‪equation of state shows a good agreement with literature.

Results

Conclusion