新穎多元鹼土硫族化合物的合成與鑑定

Abstract

在本論文中，利用固態燒結法合成出兩種鹼土硫族化合物，Ba12Sn4Se23和SrCu2SiSe4。由X光單晶繞射解析結構，並且利用理論計算驗證其鍵結與能隙。 第一部份中，在750°C 下進行燒結得到Ba12Sn4Se23，為新結構化合物，晶體晶胞為 a = 27.8351 (3) Å、b = 12.8469 (2) Å、c = 32.28653 (5) Å、β = 25.437 (12)°、V = 4959.09(17) Å3 以及Z = 4，晶系為單斜晶系 (Monoclinic)，空間群為P21/c且R1/wR2值為R1/wR2= 0.0539/0.1055。結構中包含獨立形成層狀的SnSe4四面體、填佔於層間隙地Se22-單鍵、孤立Se2-離子與鋇形成扭曲八面體結構以及+2價鋇離子組成，為Ba12(SnSe44-)4(Se22-)3(Se2-)，其他具有相似結構的結構於此討論。理論計算則顯示其具有半導體的特性，能隙為0.44 eV。 第二部份中，經由750°C 燒結流程得到SrCu2SiSe4，晶胞為a = 6.3649(17) Å、b = 6.3649(17) Å、c = 15.910(6) Å、β = 120°、V = 558.2(3) Å3以及Z = 2，晶系為三方晶系 (Trigonal)，空間群為P32，且R1/wR2 = 0.0573/0.0971。結構中包含彼此共角的CuSe4、SiSe4四面體以及+2價鍶離子，與此結構具有相同化學式之化合物亦於此進行討論，理論計算顯示其具有半導體性質，能隙為0.9 eV，能帶計算揭露其直接半導體性質，並利用COHP結果證實結構中共價鍵的存在。

Ba12Sn4Se23 and SrCu2SiSe4 were synthesized by solid-state reaction. Both of them were characterized by X-ray diffraction to define their structures. Theoretical calculations determined their density of state, band structure and crystal orbital hamilton population (COHP). Ba12Sn4Se23 crystallizes in monoclinic space group P21/c (No. 14). With a = 27.8351 (3) Å, b = 12.8469 (2) Å, c = 32.28653 (5) Å, β = 25.437 (12)°, V = 4959.09(17) Å3 and Z = 4. The final R values are R1=0.0539, wR2=0.1055. The structure contains SnSe4 tetrahedral, diselenide Se22-, isolated Se2- anion and Ba2+. Can be written in Ba12 (SnSe44-)4(Se22-)3(Se2-). Calculation of electronic structure shows semiconductor behavior with band gap 0.44 eV. SrCu2SiSe4 crystallizes in trigonal space group P3¬2 (No. 145). With a = 6.3649(17) Å、b = 6.3649(17) Å、c = 15.910(6) Å、β = 120°,V = 558.2(3) Å3 and Z = 2. The final R values are R1=0.0573, wR2=0.0971. SrCu2SiSe4 is build up by corner-sharing CuSe4 and SiSe4 tetrahedral form a three-dimensional network. With the oxidation state of Sr is 2+. Theoretical calculation indicates the semiconductor behavior with band gap 0.9 eV.