The molecular potential energy surface and vibrational energy levels of methyl fluoride. Part II.
New analytical bending and stretching, ground electronic state, potential energy surfaces for CH(3)F are reported. The surfaces are expressed in bond-length, bond-angle internal coordinates. The four-dimensional stretching surface is an accurate, least squares fit to over 2000 symmetrically unique ab initio points calculated at the CCSD(T) level. Similarly, the five-dimensional bending surface is a fit to over 1200 symmetrically unique ab initio points. This is an important first stage towards a full nine-dimensional potential energy surface for the prototype CH(3)F molecule. Using these surfaces, highly excited stretching and (separately) bending vibrational energy levels of CH(3)F are calculated variationally using a finite basis representation method. The method uses the exact vibrational kinetic energy operator derived for XY(3)Z systems by Manson and Law (preceding paper, Part I, Phys. Chem. Chem. Phys., 2006, 8, DOI: 10.1039/b603106d). We use the full C(3v) symmetry and the computer codes are designed to use an arbitrary potential energy function. Ultimately, these results will be used to design a compact basis for fully coupled stretch-bend calculations of the vibrational energy levels of the CH(3)F system.
Manson
Steven A
SA
Chemistry Department, University of Aberdeen, Meston Walk, Aberdeen AB24 3UE, UK.
Law
Mark M
MM
Atkinson
Ian A
IA
Thomson
Grant A
GA
D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003198:Computer Simulation; D006845:Hydrocarbons, Fluorinated / Q000737:chemistry*; D007700:Kinetics; D013499:Surface Properties; D013816:Thermodynamics; D014732:Vibration
D006845:Hydrocarbons, Fluorinated; C029999:fluoromethane