Читать книгу Computational Methods in Organometallic Catalysis - Yu Lan - Страница 32

For anions or molecules with many adjacent lone pairs, the basis set must be augmented with diffuse functions to allow the electron density to expand into a larger volume. For split‐valence basis sets, this is designated by “+” as in 6‐31+G(d). The diffuse functions added are a full set of additional functions of the same type as are present in the valence space. So, for carbon, the diffuse functions would be an added s basis function and a set of p basis functions. If a molecule involving hydride, diffuse functions for hydrogen atom is necessary, which would be an added s basis function, the corresponding split‐valence basis set can be written as 6‐31++G(d).