Pompe, Constantin and Preitschaft, Christian and Weihrich, Richard and Pfitzner, Arno (2015) Na2TeS3, Na2TeSe3-mP24, and Na2TeSe3-mC48: Crystal Structures and Optical and Electrical Properties of Sodium Chalcogenidotellurates(IV). INORGANIC CHEMISTRY, 54 (23). pp. 11457-11464. ISSN 0020-1669, 1520-510X
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Pure samples of Na2TeS3 and Na2TeSe3 were synthesized by the reactions of stoichiometric amounts of the elements Na, Te, and Q (Q = S, Se) in the ratio 2:1:3. Both compounds are highly air- and moisture-sensitive. The crystal structures were determined by single-crystal X-ray diffraction. Yellow Na2TeS3 crystallizes in the space group P2(1)/c. Na2TeS3 exists in a low-temperature modification (Na2TeSe3-mP24, space group P2(1)/c) and a high-temperature modification (Na2TeS3-mC48, space group C2/c); both modifications are red. Density functional theory calculations confirmed the coexistence of both modifications of Na2TeS3 because they are very close in energy (Delta E = 0.18 kJ mol(-1)). To the contrary, hypothetic Na2TeS3-mC48 is significantly less favored (Delta E = 1.8 kJ mol(-1)) than the primitive modification. Na2TeS3 and Na2TeS3-mP24 are isotypic to Li2TeS3, whereas Na2TeS3-mC48 crystallizes in its own structure type, which was first described by Eisenmann and Zagler. The title compounds have two common structure motifs. Trigonal TeQ(3) pyramids form layers, and the Na atoms are surrounded by a distorted octahedral environment of chalcogen atoms. Raman spectra are dominated by the vibration modes of the TeQ(3) units. The activation energies of the total conductivity of the title compounds range between 0.68 eV (Na2TeS3) and 1.1 eV (Na2TeS3). Direct principal band gaps of 1.20 and 1.72 eV were calculated for Na2TeS3 and Na2TeS3, respectively. The optical band gaps are in the range from 1.38 eV for Li(2)TeSe3 to 2.35 eV for Na2TeS3.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | INITIO MOLECULAR-DYNAMICS; TOTAL-ENERGY CALCULATIONS; WAVE BASIS-SET; SPECTROSCOPIC CHARACTERIZATION; BARIUM THIOTELLURITE; (CUI)(3)CU2TES3; CHALCOGENIDES; CUCLCU2TES3; DIFFRACTION; HALIDES; |
| Subjects: | 500 Science > 540 Chemistry & allied sciences |
| Divisions: | Chemistry and Pharmacy > Institut für Anorganische Chemie > Chair Prof. Dr. Arno Pfitzner Chemistry and Pharmacy > Institut für Anorganische Chemie > Arbeitskreis Dr. Richard Weihrich |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 29 Apr 2019 09:10 |
| Last Modified: | 29 Apr 2019 09:10 |
| URI: | https://pred.uni-regensburg.de/id/eprint/4298 |
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