Analytical fitting of potential energy surfaces for the Hxy systems

Use of the London‐Eyring‐Polanyi + 3‐Center + power‐series ( LEP ‐3 C ‐ PS ) analytical potential as a fit to potential energy surfaces ( PES ) which are known numerically only are suggested. This analytical fit was performed for the diatomics‐in‐molecules + 3 Center ( DIM ‐3 C ) PES of HCl 2 and HI 2 systems. The HCl 2 analytical LEP ‐3 C‐PS potential was used for classical trajectory calculations of the Cl' + HCl → HCl' + Cl reaction. The rate constant obtained from these calculations for T = 358° K is 1.95 X 10 9 cm 3 /mol sec which is close to the experimental value of 2.5 10 9 cm 3 /mol sec.