Large Basis Sets, Dissociation Energy and Geometry Optimisation
3. Large Basis Sets, Dissociation Energy and Geometry Optimisation#
Albeit deceptively small and simple, the H\(_2\) molecule with its two protons and two electrons is already too big to derive an analytic solution of the Schrödinger equation. However, one may construct a special basis set that is arbitrarily close to the complete basis set limit, and then run a post-Hartree Fock calculation. Using such techniques, it was found that, for the H\(_2\) molecule, \(E_{exact} = -1.174474{}\) a.u.
In this set of exercises, you will compare the influence of basis sets on the energy of H\(_2\) at equilibrium distance, and you will then go on to compute the dissociation energy of H\(_2\) using Hartree Fock.
Subsequently, you will determine the equilibrium geometry of a species using the example of water.
🎯 Learning goals
Influence of basis sets
Geometry optimization procedure
Basics of HF theory: RHF vs UHF
📖 Chapter in script
Chapter 3 - Basis functions in quantum chemistry
Chapter 4 - An introduction to Hartree Fock theory