Structural and Vibrational Study of Pseudocubic CdIn₂Se₄ under Compression

Abstract

We report a comprehensive experimental and theoretical study of the structural and vibrational properties of α-CdIn 2 Se 4 under compression. Angle-dispersive synchrotron x-ray diffraction and Raman spectroscopy evidence that this ordered-vacancy compound with pseudocubic structure undergoes a phase transition (7 GPa) towards a disordered rocksalt structure as observed in many other ordered-vacancy compounds. The equation of state and the pressure dependence of the Raman-active modes of this semiconductor have been determined and compared both to ab initio total-energy and lattice dynamics calculations and to related compounds. Interestingly, on decreasing pressure, at ~ 2 GPa, CdIn 2 Se 4 transforms into a spinel structure which, according to calculations, is energetically competitive with the initial pseudocubic phase. The phase behaviour of this compound under compression and the structural and compressibility trends in AB 2 Se 4 selenides are discussed.

Pressure-induced order–disorder transitions in β-In2S3: an experimental and theoretical study of structural and vibrational properties

“…This mode is usually the strongest peak of the Raman spectrum in tetrahedrally-coordinated Ga-based OVCs, and it is also notably strong in CdIn 2 Se 4 near 133 cm -1 . 94 Thanks to our lattice dynamics calculations and with the use of the J-ICE visualizer, 95 we have found that the breathing mode in β-In 2 S 3 is the 𝐵 silent mode at 296.86 cm -1 . The silent nature of this mode explains why the breathing mode is entirely absent in the Raman spectrum of β-In 2 S 3 .…”

“…8) is similar to those observed in many OVCs, like Ga 2 S 3 , 67 93 and CdIn 2 Se 4 . 94 However, these OVCs exhibit phonon gaps between low-frequency modes (with negligible or negative pressure coefficients) and highfrequency modes (with positive pressure coefficients) that are not observed in β-In 2 S 3 . As can be observed in Fig.…”

Combined Experimental and Theoretical Studies: Lattice-Dynamical Studies at High Pressures with the Help of Ab Initio Calculations

“…In general, there is a good agreement between the experimental and theoretical results on structural, vibrational, and optical properties as far as pressure-induced disorder is not crucial in the LP range. The excellent agreement of experimental and theoretical results allowed us to discuss the lattice dynamical properties of these semiconductors [8][9][10]12,13] in analogy with zincblende-type semiconductors (see Figure 2). The lack of agreement between the experimental and theoretical pressure dependence of the direct bandgap energy above certain pressure has allowed us to discuss the ranges of the pressure-induced disorder process that OVCs undergo prior to their transformation to the disorder rocksalt structure at HP (in analogy with zincblende-type semiconductors).…”

“…We have published some joint experimental and theoretical studies on structural, vibrational, and optical properties of adamantine OVCs under compression [7][8][9][10][11][12][13][14]. In general, there is a good agreement between the experimental and theoretical results on structural, vibrational, and optical properties as far as pressure-induced disorder is not crucial in the LP range.…”

HgGa2Se4 under high pressure: An optical absorption study

“…High‐pressure studies of OVCs with A II B 2 III X 4 VI stoichiometry are receiving increasing attention in the last years . The vast majority of these works have been focused on the study of the structural and vibrational properties of A II B 2 III X 4 VI compounds by means of X‐ray diffraction (XRD) and Raman scattering (RS) measurements, respectively.…”