Scale factors for carbonyl vibrational frequencies: A study of partial hessian approximation

This study investigated the use of partial Hessian approximation and bulky ligand replacement on the carbonyl stretching frequency of transition metal carbonyl complexes. Ligand replacement speeds up the frequency calculation, but also affects the vibrational frequency, due to the difference in electron donating-withdrawing strength and the steric effect. The use of a partial Hessian approximation was shown to reduce computing time without affecting the result. The scale factors for the carbonyl stretching frequencies for seven density functionals and basis sets under the partial Hessian approximation were evaluated. These factors allow experimentalists to predict and characterize the infrared spectrum of large transition metal carbonyl complexes and clusters.