Polarized Raman scattering from oriented single crystals of A2BX4 halides (A = Cs,B = Zn,X = Cl,Br, I) |
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| Affiliation: | 1. Department of Electrical and Electronics Engineering, Ballari Institute of Technology & Management, Bellary-583 104, India;2. Department of Physics, Ballari Institute of Technology & Management Bellary-583 104, India;3. Department of Instrumentation and Control, Manipal Institute of Technology, Manipal- 576104, India;4. Department of Materials Science, Gulbarga University, Gulbarga-585 106, India;5. Godu Tai Engineering college for Women,Gulbarga-585102, India;1. Kyushu Institute of Technology, 2-4 Hibikino, Wakamatsu, Kitakyushu, Fukuoka 808-0196, Japan;2. Department of Applied Chemistry, Graduate School of Engineering, Tohoku University, 6-6-07 Aoba, Aramaki, Aoba-ku, Sendai 980-8579, Japan;3. Tokuyama Corp., 1-1 Mikage-cho, Shunan-shi, Yamaguchi 745-8648 Japan |
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| Abstract: | ![]()
Raman spectra of isostructural tetrahalozincates viz. Cs2ZnI4, Cs2ZnBr4 and Cs2ZnCl4 single crystals have been measured in various scattering orientations using polarized laser excitation. The lattice dynamics of the crystals is probed down to 70 K in order to cover the successive phase sequences. Except Cs2ZnI4, none of the other salts shows the characteristic commensurate-incommensurate features of lattice instabilities. The unit cell dynamics is understood in terms of 84 phonon branches originating from various internal modes of tetrahedral ZnX2−4 group and external lattice modes. The enormous splittings, responsible for a complete loss of degeneracy in the internal modes for all the three salts, suggest a considerable distortion particularly at low temperatures in the tetrahedral geometry of the ZnX2−4 group. |
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