An ab Initio Calculation of a Six-Dimensional Potential Surface for the HCl Dimer

✍ Scribed by P.C. Gomez; P.R. Bunker

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 318 KB
• Volume: 168
• Category: Article
• ISSN: 0022-2852
• DOI: 10.1006/jmsp.1994.1297

✦ Synopsis

In an earlier paper (P. C. Gomez, P. R. Bunker. A. Karpfen, and H. Lischka, J. Mol. Spectrosc. 166, 44I-448, 1994) we calculated three-dimensional (a b) initio potential energy surfaces for the (\mathrm{HCl}) dimer at five different values of the dimer stretching coordinate (R) (the two (\mathrm{HCl}) bond lengths were held fixed) and used those potentials in a calculation of the vibrational energies involving the four large-amplitude modes. We made an adiabatic separation of the dimer stretching coordinate (R) in determining the vibrational energies. In the present paper, we calculate the energies without making the adiabatic approximation to separate (R), and we also calculate the variation of the potential energy with (\mathrm{HCl}) bond lengths. We use these ab initio results to determine the (\mathrm{HCl}) stretching frequencies as a function of the values of the four large-amplitude coordinates and hence generate an effective four-dimensional large-amplitude potential for the (\left(v_{1}=0, v_{2}=0\right.) ) (\mathrm{HCl}) stretching state. We calculate the vibrational energies for this surface. (c) 1994 Academic Press, Inc.