Statistical strained-tetrahedron model of local ternary zinc blende crystal structures

• Published in: Физика низких температур
• Date: 2004
• Main Authors: Robouch, B.V., Sheregii, E.M., Kisiel, A.
• Format: Article
• Language: English
• Published: Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України 2004
• Subjects: Фазовые переходы и структура полупроводниковых соединений
• Online Access: https://nasplib.isofts.kiev.ua/handle/123456789/120342
• Journal Title: Digital Library of Periodicals of National Academy of Sciences of Ukraine
• Cite this: Statistical strained-tetrahedron model of local ternary zinc blende crystal structures / B.V. Robouch, E.M. Sheregii, A. Kisiel // Физика низких температур. — 2004. — Т. 30, № 11. — С. 1225–1234. — Бібліогр.: 18 назв. — англ.

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 (∆fH₀) equal or
 quasi-equal. Beyond these limits predictions of such models become unreliable, in particular, when
 the ternary exhibits site occupation preferences. The strained-tetrahedron model, free from rigidity
 and stochastic limitations, was developed to better describe and understand the local structure
 of ternary zinc blende crystals, and interpret experimental EXAFS and far-IR spectra. It considers
 five tetrahedron configurations with the shape and size distortions characteristic of ternary zinc
 blende alloys, allows nonrandom distributions and, hence, site occupation preferences, conserves
 coordination numbers, respects stoichiometry, and assumes that next-neighbor values determine
 preferences beyond next-neighbor. The configuration probabilities have three degrees of freedom.
 The nineteen inter-ion crystal distances are constrained by tetrahedron structures; to avoid destructive
 stresses, we assume that the average tetrahedron volumes of both sublattices relax to
 equal values. The number of distance free-parameters ≤ 7. Model estimates, compared to published
 EXAFS results, validate the model. Knowing the configuration probabilities, one writes the dielectric
 function for far-infrared absorption or reflection spectra. Constraining assumptions restrict
 the number of degrees of freedom. Deconvolution of the experimental spectra yields site-occupation-
 preference coefficient values and/or specific oscillator strengths. Validation again
 confirms the model.