Scalable Ab Initio Electronic Structure Methods with Near Chemical Accuracy for Main Group Chemistry

This study evaluates the precision of widely recognized
quantum
chemical methodologies, CCSD(T), DLPNO–CCSD(T), and localized
ph-AFQMC, for determining the thermochemistry of main group elements.
DLPNO–CCSD(T) and localized ph-AFQMC, which offer greater scalability
compared to canonical CCSD(T), have emerged over the past decade as
pivotal in producing precise benchmark chemical data. Our investigation
includes closed-shell, neutral molecules, focusing on their heat of
formation and atomization energy sourced from four specific small
molecule data sets. First, we selected molecules from the G2 and G3
data sets, noted for their reliable experimental heat of formation
data. Additionally, we incorporate molecules from the W4–11
and W4–17 sets, which provide high-level theoretical reference
values for atomization energy at 0 K. Our findings reveal that both
DLPNO–CCSD(T) and ph-AFQMC methods are capable of achieving
a root-mean-square deviation of less than 1 kcal/mol across the combined
data set, aligning with the threshold for chemical accuracy. Moreover,
we make efforts to confine the maximum deviations within 2 kcal/mol,
a degree of precision that significantly broadens the applicability
of these methods in fields such as biology and materials science.