The strength of a chemical bond can be defined as the change in enthalpy when a bond is homolytically broken into two radicals. Bond dissociation energy is thus the measure of the strength of a bond and, while it is temperature dependent, it can be calculated by DFT or ab initio methods. In this tutorial we’re going to calculate the C-H bond dissociation energy (BDE) in the methane (CH4) molecule, one of the strongest aliphatic bonds in organic chemistry. To that end, we start from the geometry.