| A software package was developed for the ab initio solution of the multidimensional, adiabatic vibrational Schrodinger equation (VSE), using the finite element method (FEM). The package is extended and improved with a point-wise PES evaluation as well as a revised routine for computation of the Wilson G matrix on scattered surfaces. The weak formulation of the VSE requires the potential energy surface (PES) to be evaluated at specific locations based on the FEM discretization. Recent developments in automated PES generation result in two different interpolation schemes available in the package: second degree interpolating moving least squares and Kriging interpolation with variogram parameter tuning and optimized cluster size. A significant improvement has been made to the Wilson G matrix evaluation, where rotational discrepancies for planar and symmetrical molecules are removed before imposing the Eckart conditions. The new algorithm is adapted to scattered surfaces, which assures no information is lost during the transformation from Cartesian to internal coordinates. The entire package has been fully automated and made available as a web-based, platform-independent solver. In addition to the above mentioned improvements the solver was used to perform vibrational analyses on two molecular systems: the lowest excited state 2pi g of ZnCl2+and the X 2A' ground state of HC3O carbon chain free radical. Both species exhibit a strongly anharmonic PES, with two non-equivalent minima separated by a small energy barrier, which makes them ideal candidates for FEM-based probing. The solver has also been used for explicit quantum mechanical solution of the partition function of hydroxyacetaldehyde internal rotors. i. |
