This assignment is based on JSSC 2019, 269, 553-557. A link to this paper is included in the web resources.
This assignment allows students to take single crystal X-ray diffraction data and build a unit cell. Students then examine the differences between their unit cell composition and experimentally determined chemical composition. Based on the differences between these two formulas they will derive structural disorder information such as partial site occupancies within the extended solid. Students then break down the extended solid structure via molecular coordination around selected sites. Finally, students use periodic trends to make correlations between the existing structure and a related composition.
(1) Students will be able to generate the crystal structure in VESTA using tabulated single crystal X-ray data (https://jp-minerals.org/vesta/en/)
(2) Students will be able to look at a crystallographic unit cell figure and derive
- chemical composition
- stru(ctural disorder such as atomic partial occupancies
- coordination spheres around independent sites
(3) Students will be able to utilize periodic trends to predict structural correlations.
Computer, VESTA (https://jp-minerals.org/vesta/en/)
Students should have some knowledge of extended solids and how the unit cell and empirical formula relate to one another. Additionally, one main concept that is being exercised is the idea of atomic vacancies within a structure; atomic site occupancies are some fraction of a whole number because of some sites being partially unoccupied.
This assignment is based on the data presented in Table 1, Table 2, Figure 1, and the elemental analysis (section 2.2). Students will have the opportunity to implement softwares, such as VESTA, Mercury, or Olex2, to build a unit cell from raw crystallographic data (.cif). The cif can be downloaded here if that is beyond the scope of your course, and it can be readily viewed in Mercury or Olex2. A manual for VESTA has been provided under the web resources section. The cif can be loaded directly or structural information can be entered manually via "File", "New Structure." In addition a youtube tutorial has been provided under web resources.
This should be evaluated based on students ability to answer the posted questions.
This has yet to be implemented in a classroom setting.