The reliability of modeling ions or polar molecules by point charges is investigated from the point of view of possible non-physical variational distortions of the molecular wavefunction. Mathematical and observable-based criteria are given to monitor the extent of variational distortions. A model system of two H2molecules and a cation is studied, allowing investigation of large basis sets. The unphysical distortion, which tends to be worse as the basis set increases, is already observed in split-shell quality bases, if sensitive parameters (e.g. van der Waals distances) are investigated. It has a negligible influence on less sensitive molecular properties, such as the total electron density, even in large basis sets.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Condensed Matter Physics
- Atomic and Molecular Physics, and Optics
- Surfaces and Interfaces