Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada.
Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, People's Republic of China.
Inorg Chem. 2023 May 15;62(19):7491-7502. doi: 10.1021/acs.inorgchem.3c00786. Epub 2023 Apr 28.
Complete substitution of Li atoms for Ag atoms in AgGaSe and AgInSe was achieved, resulting in the solid solutions LiAgGaSe and LiAgInSe. The detailed crystal structures were determined by single-crystal X-ray diffraction and solid-state Li nuclear magnetic resonance spectroscopy, which confirm that Li atoms occupy unique sites and disorder only with Ag atoms. The tetragonal CuFeS-type structure (space group 4̅2) was retained within the entirety of the Ga-containing solid solution LiAgGaSe, which is noteworthy because the end-member LiGaSe normally adopts the orthorhombic β-NaFeO-type structure (space group 2). These structures are closely related, being superstructures of the cubic sphalerite and hexagonal wurtzite prototypes adopted by diamond-like semiconductors. For the In-containing solid solution LiAgInSe, the structure transforms from the tetragonal to orthorhombic forms as the Li content increases past = 0.50. The optical band gaps increase gradually with higher Li content, from 1.8 to 3.4 eV in LiAgGaSe and from 1.2 to 2.5 eV in LiAgInSe, enabling control to desired values, while the second harmonic generation responses become stronger or are similar to those of benchmark infrared nonlinear optical materials such as AgGaS. All members of these solid solutions remain congruently melting at accessible temperatures between 800 and 900 °C. Electronic structure calculations support the linear trends seen in the optical band gaps and confirm the mostly ionic character present in Li-Se bonds, in contrast to the more covalent character in Ga-Se or In-Se bonds.
实现了 Li 原子对 AgGaSe 和 AgInSe 中 Ag 原子的完全取代，生成了 LiAgGaSe 和 LiAgInSe 固溶体。通过单晶 X 射线衍射和固态 Li 核磁共振波谱确定了其详细晶体结构，证实 Li 原子占据独特的位置，仅与 Ag 原子无序分布。在整个 Ga 含量的固溶体 LiAgGaSe 中保留了四方 CuFeS 型结构（空间群 4̅2），这是值得注意的，因为端元 LiGaSe 通常采用正交β-NaFeO 型结构（空间群 2）。这些结构密切相关，是立方闪锌矿和六方纤锌矿原型的超结构，被类似金刚石的半导体采用。对于 In 含量的固溶体 LiAgInSe，随着 Li 含量超过 = 0.50，结构从四方相转变为正交相。光学带隙随着 Li 含量的增加逐渐增加，LiAgGaSe 从 1.8 到 3.4 eV，LiAgInSe 从 1.2 到 2.5 eV，从而可以控制到所需的值，同时二次谐波产生响应变得更强或类似于 AgGaS 等基准红外非线性光学材料。这些固溶体的所有成员在 800 到 900°C 之间的可访问温度下仍保持一致熔化。电子结构计算支持光学带隙的线性趋势，并证实了 Li-Se 键中存在主要的离子特性，与 Ga-Se 或 In-Se 键中的更共价特性形成对比。
