Statistical analysis of inter-ionic distances and occupation preferences in ternary zincblende and wurtzite structured crystals

摘要

The statistical strained-tetrahedron model was developed to overcome two common assumptions of previous models: 1) rigid undistorted ion sublattice of regular tetrahedra throughout all five configurations and 2) random ion distribution. These simplifying assumptions restrict the range of applicability of the models to a narrow subset of ternary alloys for which the constituent binaries have their lattice constants and standard molar enthalpies of formation (Δ_fH_0) equal or quasi-equal. Beyond these limits predictions of such models become unreliable, in particular, when the ternary exhibits site occupation preferences (SOPs). The strained-tetrahedron model, free from rigidity and stochastic limitations, was first developed to interpret structural information obtained with the use of x-ray absorption experimental data. It was validated on published EXAFS data of both zincblende (ZB) and intermetallide materials. The model was then extended to describe and interpret infrared spectra. The derivation and verification of the validity of our model and its assumptions are detailed in our published papers. We extend the model to cover the interpretation of far IR spectra and successfully apply it to a set of GaAs_yP_(1-y) spectra. The unfolding gives the SOP coefficient values andor specific oscillator strengths (OSs). Comparison with data available in the literature showed the good agreement of our model predictions.