Knowledge Bank

We present accurate potential energy surface for Ar--HF, $Ar--H2O$, and $Ar--NH3$ from the supermolecular calculations using M""{o} Sller-Plesset perturbation theory up to the complete fourth-order (MP4) and efficient basis sets containing bond functions. The calculations on Ar-HF with a fixed HF bond length of $r=[r)\nu =0$ give a global potential minimum with a well depth of $200.0cm-1$ at the position $R=3.470\backslash AA,\theta =0\circ$ (linear Ar-H-F) a secondary minimum with a well depth of $881.cm-1$ at $R=3.430\backslash AA\theta =180\circ$ (linear Ar-F-H) and a potential barrier f $128.3cm-1$ that separates the two minima near $R=3.555\backslash AA,=90\circ$ (T shaped). Further calculations on the three main configurations of Ar-HF with varying HF bond length are carried out to obtain vibrationally averaged well depths for $\nu$ =0,1,2 ad 3. Our primary wells are about $15cm-1$ higher than those of Hutson’s H6(4,3,2) $potential1$ for $\nu$ =0,1,2 ad 3, and our minimum distances are about 0.05 {\AA} longer. The intermolecular potentials of $Ar-H2O$ and $Ar-NH3$ are calculated with the monomers held fixed at equilibrium geometry. The calculations on $Ar-H2O$ give a single global minimum with a well depth of $130.2cm-1$ at $R=3.603\backslash AA,\nu =75\circ ,\theta =0\circ$, along with barriers of 22.6 and $26.6cm-1$ for in-plane rotaion at $\theta =0\circ$, and $180\circ$ respectively, and a barrier of $52.6cm-1$ for out-of-plane rotation at $\theta =90\circ ,\theta =90\circ$. All these agree well with experiment, especially with the recent AW2 $potential.2$ The calculations on $Ar-NH3$ give a single global minimum with a well depth of $130.1cm-1$ at $R=3.628\backslash AA,\theta =90\circ$. All these agree well with experiment, especially with the recent AW2 $potential.2$ The calculations on $Ar-NH3$ give a single global minimum with a well depth of $130.1cm-1$ at $R=3.628\backslash AA,\theta =90\circ ,\theta =60\circ$, along with barriers of 55.2 and $38.0cm-1$ for end-over-end rotation at $\theta =0\circ$ and $180\circ$ respectively, and a barrier of $26.6cm-1$ for rotation about $NH3$ symmetry axis at $\theta =90\circ ,\varphi =0\circ$. Again, all these agree with $experiment.3$