Force constant refinement in cartesian coordinates

Abstract

The recently increasing interest in physically reliable force fields leads to a revisiting of applied computational methods. The combination of ab initio calculations and experimental information or the application of parametric methods is discussed extensively (ref. 1,2). Force constant refinement in cartesian coordinates offers several advantages in comparison with the much more familiar methods using internal (symmetry) coordinates: The formalism for solving the vibrational eigenvalue problem and the iterative matching of calculated to observed eigenvalues is very clear, the received eigenvectors seem to be physically meaningful and well suited for intensity calculations using quantum chemical methods. To examine the capability of the proposed method calculations have been carried out on Trimethylphosphineoxide-compounds. Metal-bis-diethyldithiocarbamate — complexes and Thiophene.