Exercise 7

Part of the course Computational Chemistry.

Quantum Chemistry calculations are at the heart of many modern research works. They allow a glimpse into the processes at atomistic level that often is not accessible by an experiment. That comes at a price: computations take time and often require expert knowledge to extract reliable data. The exercises are meant to give you an idea of how to run calculations and how to extract basic information. Later ones will give you an intuition of the impact of critical settings.

Task 7.1: C'mon, Do Something

Read the PySCF quickstart page and write a function get_n2_dimer_energy(distance) to obtain, well, the energy of a nitrogen dimer at a certain distance. Use this function to determine the minimum energy distance. Use Hartree-Fock with the 6-31G basis set.

Note: these settings are not reliable and are only used for demonstration purposes. Please do not use them in actual research unless you know what you are doing.

Task 7.2: Ups and Downs

Write a function fit_n2_morse_potential() to fit a Morse potential to data you got from task 1 in the vicinity of the minimum. Visualize the two profiles. What do you observe?

Task 7.3: Pushing the Limits

Calculate the dissociation profile of the Nitrogen dimer using the code you wrote by calling the function get_n2_dimer_energy(distance) in small steps e.g. 0.01 Angstrom and plot the resulting curve. What do you observe? Can you explain what is happening?