Reduced Serially Improved GTOs for Molecular Applications from H to Ar: Efficient Diffuse Functions in Augmented Basis Sets.

A new family of Serially Improved Gaussian-type Orbitals for Molecular Applications (SIGMA) has been developed for hydrogen to argon and is available in both standard and augmented versions. This new basis set features a reduced number of primitive functions compared to the original SIGMA set and eliminates the constraint of shared exponents across different angular momentum shells. Its composition is similar to that of the Dunning correlation-consistent basis sets. In the augmented version of this novel SIGMA family, termed reduced SIGMA, the diffuse primitive functions are contracted with others bearing higher exponents, unlike in the corresponding Dunning sets, where they are added to the set without contraction. This feature makes the reduced SIGMA basis sets less susceptible to linear dependencies in large and compact systems, which is reflected in better convergence of the minimization process and has a positive impact on energy optimization procedures. The improved performance of the augmented reduced SIGMA basis sets over Dunning and other commonly used basis sets is demonstrated through atomic and molecular calculations at various computational levels across a broad set of systems.