A Quadratic Pair Atomic Resolution of the Identity Based SOS-AO-MP2 Algorithm Using Slater Type Orbitals

We report a production level implementation
of pair atomic resolution
of the identity (PARI) based second-order Møller–Plesset
perturbation theory (MP2) in the Slater type orbital (STO) based Amsterdam
Density Functional (ADF) code. As demonstrated by systematic benchmarks,
dimerization and isomerization energies obtained with our code using
STO basis sets of triple-ζ-quality show mean absolute deviations
from Gaussian type orbital, canonical, basis set limit extrapolated,
global density fitting (DF)-MP2 results of less than 1 kcal/mol. Furthermore,
we introduce a quadratic scaling atomic orbital based spin-opposite-scaled
(SOS)-MP2 approach with a very small prefactor. Due to a worst-case
scaling of O(N3), our implementation is very fast already
for small systems and shows an exceptionally early crossover to canonical
SOS-PARI-MP2. We report computational wall time results for linear
as well as for realistic three-dimensional molecules and show that
triple-ζ quality calculations on molecules of several hundreds
of atoms are only a matter of a few hours on a single compute node,
the bottleneck of the computations being the SCF rather than the post-SCF
energy correction.