Fully-Optimized Parameters for Mixed Ramp-Gaussian Basis Sets

The description of core electrons is important for calculating
a number of chemical properties using computational quantum chemistry.
Though many existing specialized all-Gaussian basis sets for core-dependent
properties out-perform general-purpose all-Gaussian basis sets, the
underlying deficiencies of Gaussian basis sets when describing the
core region of the electronic wave function persist, which limits
accuracy and increases computational cost. A promising alternative
to traditional all-Gaussian basis sets are mixed ramp-Gaussian basis
sets. Previous investigations which focused on simply replacing core
basis functions with ramp functions failed to provide the anticipated
improvements in performance. For the first time, we present parametrizations
for fully optimized mixed ramp-Gaussian basis sets in the form of
the RS‐n basis sets. Using pseudo ramp functions
to approximate the ramps, basis set performance for these new mixed
ramp-Gaussian basis sets is evaluated. Through multiple benchmark
studies, the importance of fully optimizing the nonpolarization Gaussian
functions in mixed ramp-Gaussian basis sets is confirmed. These investigations
also show mixed ramp-Gaussian basis sets to have significant promise
for the efficient calculation of core-dependent properties.