First-principles calculations on structure and elasticity of wurtzite-type indium nitride under pressure

Abstract

First-principles calculations of the crystal structures, and elastic properties of wurtzite-type indium nitride (w-InN) have been carried out with the plane-wave pseudopotential density functional theory method. The calculated values (for crystal structures) are in very good agreement with experimental data as well as with some of the existing model calculations. The dependence of the elastic constants c_ij, the aggregate elastic modulus (B, G, E), and the elastic anisotropy on pressure have been investigated. Moreover, the variation of the Poisson ratio, Debye temperature, and the compressional and shear elastic wave velocities with pressure P up to 10 GPa at 0 K have been investigated for the first time.

Introduction

Group-III nitrides have attracted considerable attention during the past decade due to their promising technological applications in the optoelectronic and electronic devices [1], [2], [3]. Indium nitride crystallizes as a hexagonal wurtzite structure under normal conditions [1], [2], [4], [5], [6], successful growth [7], [8] has also reported that InN grows in zincblende structure. Then, Serrano et al. [9], [10] confirmed that the ZB phase is indeed metastable using first-principles calculations. Theoretical studies based on total energy calculations [11], [12] clearly predicted the high pressure phase of InN is the rocksalt structure. It was confirmed experimentally [4], [13]. The subject of extensive elastic properties studies [14], [15], [16], [17], [18], [19] of InN has been fostered in recent years.

The elastic properties of a solid are important because they are closely related to various fundamental solid-state phenomena such as interatomic bonding, equations of state, and phonon spectra. Elastic properties are also linked thermodynamically with specific heat, thermal expansion, Debye temperature, and Grüneisen parameter. Most importantly, knowledge of the elastic constants is essential for many practical applications related to the mechanical properties of a solid: load deflection, thermoelastic stress, internal strain, sound velocities, and fracture toughness [20].

In 1979, Sheleg et al. [14] firstly reported the experimental elastic constants of wurtzite-type InN (w-InN) from the mean square displacements of the lattice atoms measured by X-ray diffraction. Since then, there have been several theoretical investigations on the elastic constants of w-InN at zero pressure [15], [16], [17], [18], [19]. In 1996, Kim et al. [15] presented a theoretical study of the elastic constants for the w-InN using the FP-LMTO and the tensor transformation method. Very shortly thereafter, Wright et al. [16] calculated the elastic constants of the w-InN from ab initio pseudopotentials and plane-wave method. Then, Chisholm et al. [18] and Marmalyuk et al. [17] studied the elastic constants of the w-InN utilizing empirical and theoretical approaches. Recently, Wang et al. [19] calculated the elastic constants of the w-InN applying a fundamental corresponding states relationship. However, to our knowledge, no other theoretical or experimental data of the w-InN under high pressure are yet reported.