The coupled cluster theory\ is applied to calculate the anion neutral potential of ArCl -. A scheme for constructing a very efficient basis set is proposed based on theoretical consideration. The basis set is Aug cc pVQZ (moved g functions) containing { 3s3p2d1f } bond functions. Detail CCSD(T) calculations on ArCl - give a global potential minimum with a well depth -61.17 meV at the position R =0.371 nm. This is in good agreement with experiment, especially with the piecewise Morse Switching function van der Waals (MSV) potential to fit the zero electron kinetic energy spectroscopy of the ArCl - anion. The spectroscopy is observed by Lawrence Berkeley National Laboratory.
