Knowledge Bank

Kofranek, Lischka and Karpfen have done extensive ab initio calculations on $(HF)2.\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}$ Their ab initio points have been fitted to an analytic form. Using this potential energy function tunnelling splittings have been calculated by using a reaction path model. The reaction path, the steepest descent path in mass-weighted Cartesian coordinates, has been found. If $(HF)2$ is approximated as a symmetric top $(k-0.998for(HF)2)$, it is particularly easy to calculate rotational-vibrational energy levels if the reaction coordinate is used as the large amplitude motion coordinate, because the effective moment of inertia tensor takes a very simple form.