A quantum Monte Carlo study of vibrational states of planar acetylene

This article reports the results of correlated function quantum Monte Carlo (CFQMC) calculations of the vibrational excited states of triatomic molecules, H2O, H-3(+) and HCN, and for the tetraatomic molecule of Acetylene (HCCH) restricted to vibrations on the plane. The results for the triatomic molecules are in good agreement with experiment and other calculations. We had to modify the wave functions used in other CFQMC calculations of the same kind, to account for the bending modes in the linear molecules, HCN and HCCH. The results of our calculations are in agreement with other theoretical work in the same potential energy surface and with the experimental results for the fundamental vibrational modes. (C) 1999 Elsevier Science B.V. All rights reserved.