This in-class activity is designed to assist students with the visualization of solid-state close-packed structures, using metal-sulfide nanocrystalline materials as a an example system. Students will be asked to visualize and describe both hexagonal closest packed (hcp) and cubic closest packed (ccp) structure types, and isolate the tetrahedral and octahedral holes within each structure type. Lasty, students will be asked to compare and contrast four metal-sulfide unit cells discussed in the paper below.
Powell, A.E., Hodges J.M., Schaak, R.E. Preserving Both Anion and Cation Sublattice Features during a Nanocrystal Cation-Exchange Reaction: Synthesis of a Metastable Wurtzite-Type CoS and MnSJ. Am. Chem. Soc. 2016, 138, 471-474.
In answering these questions, a student will…
- ...develop stronger visualaztion skills for extended, solid state materials;
- ...compare the packing sequence of close packed structures;
- ...locate tetrahedral and octahedral holes in close packed systems;
- ...count the number of tetrahedral / octahedral holes relative to the lattice ions; and
- …determine the number of atoms in a unit cell.
The use of software - such as the demo version of CrystalMaker (http://www.crystalmaker.co.uk) or StudioViewer (Esko - app stores) - will be really helpful. StudioViewer can be run on cell phones, tablets, or MacOS devises. CrystalMaker is available for both Mac and PC.
This learning object was developed at the 2017 MARM IONiC workshop on VIPEr and Literature Discussions. It has not yet been implemented.
This could be assigned for homework, but would likely work better in class with guidance.
Evaluation methods could include grading as an in-class worksheet, trading with a partner for peer grading or turned in as an out-of-class graded homework assignment.
Currently, this activity has not been tested in a classroom. Please post how your students did!