Static correlation in vibrational frequencies studied using thermally-assisted-occupation density functional theory

Abstract

Thermally-assisted-occupation density functional theory is a method that incorporates approximate static correlation at a relatively low computational cost and allows static correlation effects to be more easily incorporated into vibrational frequency calculations. Here the effects of thermally-assisted-occupation are tested on a wide range of frequencies, indicating that static correlation plays an important role in the vibrations of several molecules that make up popular test sets of experimental vibrational frequency data. Small but persistent effects are also noted for vibrations involving significant hydrogen stretching character and mode-specific differences are seen for several molecules that are known to have multi-reference character.