This is the first in a series of exercises used to teach computational chemistry. It has been adapted, with permission, from a Shodor CCCE exercise (http://www.computationalscience.org/ccce).
In the exercise, students learn about simple Gaussian-type basis sets. In an Excel spreadsheet, they compare the Slater function for a 1s orbital to the combination of one, two, or three Gaussian functions. They are also introduced to the Basis Set Exchange website (https://bse.pnl.gov/bse/portal).
After completing this exercise, students will be able to:
- Explain why Gaussian-type orbitals (GTOs) are used instead of Slater-type orbitals (STOs) in computational chemistry.
- Use Excel to model the hydrogen STO with GTOs.
- Explain why combining multiple GTOs produces a better approximation of an STO.
- Find alpha values for the STO-3G basis set in an online database.
Students need access to a computer, the internet, and Excel. I initially taught this part of the course in a computer lab, but last year all of the students were able to bring their own laptops. I bring an extra laptop to class just in case.
All of the students had some experience with Excel in their general chemistry course. However, entering the complicated equations into Excel is challenging for many of them. I have found it most effective to simply allow them to help one another with this.
They are typically able to make the graphs without extra assistance, but I walk around the class and help as needed.
I ask the students to bring printed copies of their graphs and answers to the questions in the student handout to the next class. I collect these and check them for completeness (credit/no credit).
Because the students completed the exercise during the previous class, their work is typically complete and correct.