Stability of wurtzite, unbuckled wurtzite, and rocksalt phases of SiC, GaN, InN, ZnO, and CdSe under loading of different triaxialities

作者：Sarasamak K^*; Kulkarni A J; Zhou M; Limpijumnong S

来源：Physical Review B, 2008, 77(2): 024104.

DOI：10.1103/PhysRevB.77.024104

First principles calculations are carried to study the structural stability of SiC, GaN, InN, ZnO, and CdSe which are found to transform from a fourfold coordinated wurtzite (WZ) structure under ambient conditions to two different crystalline structures under loading of different triaxialities. Under hydrostatic compression, transformation into a sixfold coordinated rocksalt (RS) structure occurs, and under uniaxial compression along the [0001] direction and uniaxial tension along the [01 (1) over bar0] crystalline direction (except SiC and GaN), transformation into a fivefold coordinated unbuckled wurtzite phase (HX) is observed. The lack of the WZ -> HX transformation for SiC and GaN under uniaxial tension along the [01 (1) over bar0] direction is because for these two materials the tensile stress required for the enthalpy of HX to become lower than the enthalpy of WZ is higher than their corresponding ultimate tensile strength. Critical stress levels for the transformations are found to depend on the formation energies of the WZ, HX, and RS structures which in turn are related to the ionicity of each material. The transformations are a manifestation of the tension-compression response asymmetry of these materials.

• 出版日期2008-1