Simplified Box Orbitals (SBO) for H To Ar atoms: Exact expressions, SBO‐3G approximations, and relations with the ZDO approximation. Issue 17 (2nd June 2016)

• Record Type: Journal Article
• Authors: García, Victor; Zorrilla, David; Sánchez‐Márquez, Jesús; Fernández‐Núñez, Manuel
• Is Part Of: International journal of quantum chemistry. Volume 116:Issue 17(2016)
• Page Start: 1303
• Page End: 1312
• Publication Date: 2016-06-02
• Subjects: spatially restricted basis functions -- zero differential overlap -- Gaussian expansion -- confined systems -- basis sets for huge systems; Quantum chemistry -- Periodicals; 541.28
• DOI: 10.1002/qua.25178
• Languages: English
• ISSNs: 0020-7608

Abstract

Abstract : Simplified Box Orbitals (SBO) are a kind of spatially restricted basis functions. SBOs have a similar use and value to Slater functions but, because they fulfill a version of the zero‐differential overlap approximation, they allow for a drastic reduction in the number of two‐electron integrals to be calculated when dealing with huge systems, and they seem to be specially adapted to study confined systems such as molecules in solution. In a previous study, the mathematical shape of SBOs was discussed and the necessary parameters were obtained by means of the variational method. In the present study, the parameters of each SBO were obtained by applying the condition that it is as similar as possible to the STO that would be used in a basis set without spatial restrictions. We have developed a method to achieve this likeness and deduced simple formulas to describe all the SBOs of any atom. We also present the SBO‐3G expansions of the SBOs obtained, making it possible to use these SBOs with standard quantum chemistry calculation software. Simple formulas were also deduced to directly write the SBOs and SBO‐3G corresponding to the atoms with a Z value of between 1 and 18. Finally, as a first example of the usefulness of this kind of functions, an optimized SBO‐3G basis set is proposed for atoms from H to Cl in molecules. © 2016 Wiley Periodicals, Inc. Abstract : Simplified Box Orbitals (SBO) are a kind of spatially restricted basis functions, whose value is zero from a certain distance to the origin, which comply with an updated version of the zero‐differential overlap (ZDO) approximation. The use of these functions allows a very important reduction of computation time for HF and DFT calculations, and yield results of equivalent quality to STO basis. They can be managed through Gaussian expansions (SBO‐nG), similarly to STO‐nG.