Measuring Student Learning of Crystal Structures Using Computer-based Visualizations

Crystal structures are foundational to many aspects of materials science, yet students often have difficulty visualizing geometric relationships in even the simplest structures. For example, many students make errors when drawing the atomic arrangements on the (110) and (111) planes in the face-centered cubic (FCC) crystal structure. We previously designed an active-learning lesson that allows students to investigate crystal structures and atomic arrangements using a computer program, OVITO. The lesson is designed for a 50-minute introductory materials science course and consists of both individual and group activities. The first part is completed individually and requires students to identify planes and basic crystal structures and then draw and rank the atomic densities of a given set of planes. The second part has students work together in small groups to visualize crystal structures using OVITO, repeating some questions from the first part. Results of the pilot study indicated that the lesson allowed many students to identify and correct mistakes in their initial drawings. In this work, we categorize and quantify the most common mistakes that students make and investigate errors that seem harder for students to identify and correct. For example, missing atoms are commonly corrected by students, while there are persistent errors in sketching which atoms are (or are not) contiguous. Based on student responses in Fall 2016, we have revised the activity to more clearly emphasize the characteristics of a correct response, and have increased the scaffolding to guide students. Additionally, the revised activity is more focused than the original, allowing students to spend more time on the reflection portion of the activity. Student performance is measured and compared in two courses at different institutions. Student responses on a concept inventory at the beginning and end of the term are also compared to investigate the development and persistence of their learning gains.