This free half-life calculator can determine any of the values in the half-life formula given three of the four values. As an example, I reran the water HF/3-21G* calculation above, with both Opt=Tight and Opt=VeryTight. This raises the question of whether the you need to use tighter convergence. is, \[ Actually, is never calculated directly in Gaussian. Access list of astrophysics formulas download page: If we use the center-of-mass frame of reference we can show easily that for a two-body system the total kinetic energy (K.E.) The reduced mass calculated for the ring-puckering vibration of 1,4-cyclohexadiene has a minimum value for the planar conformation and increases substantially as the molecule puckers. The roots of the eigenvalues are the fundamental frequencies of the molecule. I’ll outline the general polyatomic case, leaving out details for dealing with frozen atoms, hindered rotors, and the like. ,