Modeling the Geometry of Polyenes in the Ground Electronic State

The accuracy of describing the geometry of polyenes in their ground electronic state by various methods is examined. To achieve high accuracy, it is proposed to use the SCS-MP2 method, taking into account the correlation of all electrons, including core ones, and using the cc-pwCVTZ atomic basis. It is shown that, when using this approach, errors in the lengths of C–C bonds do not exceed 0.003 Å. The use of the RIJCOSX and DLPNO approximations speeds up calculations without significantly increasing the errors in bond lengths, but allows the proposed approach to be used to describe such large systems as carotenoids.