Ab initio studies of the ground‐state potential energy surface of formamide

Ab initio calculations employing a standard double‐zeta basis set augmented with various polarization functions have been used to investigate the lowest energy region of the ground‐state potential energy surface of the formamide molecule. Hartree‐Fock calculations with only d polarization functions on the nonhydrogen atoms located two stable minima, that with geometry distorted from planarity having slightly lower energy; only one stable minimum with planar structure is found when p polarization functions on the hydrogens are included. In contrast optimizations, which account approximately for the correlation energy using second‐order Møller‐Plesset perturbation theory consistently favor a single slightly nonplanar minimum energy geometry.