저차원 Niobium 칼코진 화합물의 합성과 구조
Synthesis and Structure of Low-dimensional Niobium Chalcogenides
- 주제(키워드) Niobium , Chalcogenides , Low-dimensional
- 발행기관 아주대학교
- 지도교수 윤호섭
- 발행년도 2006
- 학위수여년월 2006. 2
- 학위명 석사
- 학과 및 전공 일반대학원 화학과
- 본문언어 영어
초록/요약
The new one-dimensional binary niobium chalcogenide, Nb4S17 has been synthesized through the reaction of elements with alkali metal halide and structurally characterized by single crystal X-ray diffraction techniques. The Nb4S17 crystallizes in the space group P-1 of the triclinic system in a cell of dimensions a=16.787(4)Å, b=19.820(6)Å, c=19.828(6)Å, α=116.715(11) β=97.690(11), γ=94.473(11), V=5768(3)Å3. In this compound, three crystallographically independent one-dimensional chains composed of [NbS8] units are observed. These chains are stabilized through the van der Waals interaction of the S anions. To the best of our knowledge, this phase is the most chalcogen-rich group 5 metal binary sulfide. The new two-dimensional ternary selenide, Nb4-XTiXSe17 (x≒0.6) has been synthesized through the reaction of elements with alkali metal halide, and structurally characterized by single crystal X-ray diffraction techniques. This compound crystallizes in a monoclinic space group, C2 in a cell of dimensions, a=11.8247(8)Å, b=11.9400(8)Å, c=7.6820(5)Å, β=100.424(3), V=1066.70(12)Å3. This compound is built up from a one-dimensional chain interlinked through Se bridges. One of the metal sites is occupied by statistically disordered Nb and Ti atoms (M), whereas the other site (Nb1) is fully occupied by Nb atoms. Uranium trisulfide, US3, is isostructural with USe3, which has the ZrSe3 structure type. In the asymmetric unit, the site symmetries of the U atom and the three S atoms are m. The structure consists of two-dimensional layers that stack perpendicular to the [001] direction. Each layer comprises US8 bicapped trigonal prisms that edge share in the [100] direction and face share in the [010] direction. The compound may be described as U4+(S2)(S22-). Tetragermanium nonaselenide, Ge4Se9, adopts a two-dimensional layered structure. The layer is made up of infinite chains of corner-sharing GeSe4 tetrahedra and the chains are connected via the Ge2Se7 unit to form the two-dimensional layer. These layers are stacked to form the three-dimensional structure with a van der Waals gap. A previous structure report on Ge4Se9 based on powder diffraction data is comparable with our results except for the absolute structure determination. The structure of KNb5O13 consists of two-dimensional slabs of edge- and corner-sharing NbO6 octahedra, and these slabs are interconnected to form the three-dimensional framework. The K+ cations reside in the empty channels. Among the three crystallographically independent Nb atoms, the coordination around the Nb atom bridging the slabs is more regular than those of the other Nb atoms. A bond-valence calculation indicates that the charge balance should be represented by [K+][Nb5+]5[O2-]13.
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CONTENTS
ABSTRACT-------------------------------------------- 1
ABSTRACT (KOREAN) --------------------------------- 3
CONTENTS ------------------------------------------- 5
LIST OF TABLES -------------------------------------- 8
LIST OF FIGURES ------------------------------------- 10
INTRODUCTION -------------------------------------- 12
TEXT
Ⅰ. The Most Chalcogen-rich Group 5 Metal Binary Sulfide
Synthesis and Crystal Structure of Nb4S17 ----------- 15
1. Abstract -------------------------------------------- 15
2. Introduction ----------------------------------------- 16
3. Experimental --------------------------------------- 17
• Synthesis ------------------------------------------ 17
• Crystallographic studies ----------------------------- 17
4. Results and Discussions ---------------------------- 19
5. Tables -------------------------------------------- 21
6. Figures -------------------------------------------- 34
Ⅱ. Synthesis and Crystal Structure of a New Two-
DimensionalTernary Selenide, Nb4-XTiXSe17 (x≒0.6)- 38
1. Abstract -------------------------------------------- 38
2. Introduction ----------------------------------------- 39
3. Experimental --------------------------------------- 41
• Synthesis ------------------------------------------ 41
• Crystallographic studies ----------------------------- 41
4. Results and Discussions ---------------------------- 43
5. Tables --------------------------------------------- 45
6. Figures --------------------------------------------- 50
APPENDIX
Ⅰ. Synthesis and Crystal Structure of Uranium trisulfide,
US3 ---------------------------------------------- 53
1. Abstract ------------------------------------------- 53
2. Introduction ---------------------------------------- 54
3. Experimental -------------------------------------- 55
• Synthesis ----------------------------------------- 55
• Crystallographic studies --------------------------- 55
4. Results and Discussions --------------------------- 57
5. Tables -------------------------------------------- 58
6. Figures -------------------------------------------- 61
Ⅱ. Synthesis and Reinvestigation of Ge4Se9 based on
single-crystal data --------------------------------- 63
1. Abstract -------------------------------------------- 63
2. Introduction ----------------------------------------- 64
3. Experimental --------------------------------------- 65
• Synthesis ------------------------------------------ 65
• Crystallographic studies ----------------------------- 65
4. Results and Discussions ---------------------------- 68
5. Tables -------------------------------------------- 70
6. Figures -------------------------------------------- 74
Ⅲ . Synthesis and Crystal Structure of
a New Potassium Niobate, KNb5O13 ----------------- 77
1. Abstract -------------------------------------------- 77
2. Introduction ----------------------------------------- 78
3. Experimental --------------------------------------- 79
• Synthesis ------------------------------------------ 79
• Crystallographic studies ----------------------------- 79
4. Results and Discussions ---------------------------- 81
5. Tables -------------------------------------------- 83
6. Figures -------------------------------------------- 86
REFERENCES ---------------------------------------- 89
