Ab initio calculation of anharmonicity in the vibrational spectra of Hobo

The ab-initio MP2 and MP4-SDQT molecular energies, gradients and Hessians have been evaluated at 89 points for the ground electronic state of HOBO molecule. The corresponding potential energy surfaces have been fitted to obtain a cubic and quartic force field from which the fundamental anharmonic frequencies have been determined using a variation perturbation theory. Theoretical predictions reproduce the experimental to a degree of agreement which allows a complete assignment of all the fundamental bands of HOBO and DOBO.