Ab initio study of the ground and excited states of HCP and its isomer HPC

✍ Scribed by Elisheva Goldstein; Suqian Jin; M. Robyn Carrillo; Robert J. Cave

• Publisher: John Wiley and Sons
• Year: 1993
• Tongue: English
• Weight: 865 KB
• Volume: 14
• Category: Article
• ISSN: 0192-8651
• DOI: 10.1002/jcc.540140206

✦ Synopsis

The potential energy surface of HCP converting to HPC in its ground electronic state has been investigated with ab initiv methods at levels up to MP2/6-311G**//MP4/6-3llG** as well as TZV+ +** CASSCF. All geometries are fully optimized and compare favorably to previous theoretical and experimental values. The HCP molecule is predicted to be 85.4 kcal/mol lower in energy than its linear isomer at the MP2/6-31G*// MP2/6-31G* level. The energy barrier for hydrogen rearrangement is found to be merely 2.3 kcal from the HPC end. CASSCF studies were initiated to clarify the low barrier and lent support to a flat surface as HPC converts to stable, linear HCP at the TZV + + ** level. CASSCF also predicts that HPC is unstable with respect to bending. Harmonic vibrational frequencies for HCP results in 5% accuracy or better. A bent triplet is found to be the lowest excited state using the CASSCF method. 0 1993 by John Wiley 8, Sons, Inc.