Transcorrelated theory for transition-metal atoms

We benchmark ionization and excitation energies of transition-metal atoms Sc–Zn with a transcorrelated Hamiltonian combined with pseudopotentials. The similarity transformed Hamiltonian provides compact transcorrelation (TC) wave functions in affordable aug-cc-pVTZ and aug-cc-pVQZ Gaussian bases and eliminates the need for complete basis set extrapolations. The use of Douglas-Kroll-Hess theory is omitted because scalar relativistic effects are included in the pseudopotentials. Treating the full semicore (<a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mn>3</a:mn><a:mrow><a:mi>s</a:mi></a:mrow><a:mspace width="4pt"/><a:mn>3</a:mn><a:mrow><a:mi>p</a:mi></a:mrow></a:math>) valence and freezing only <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"><c:mn>1</c:mn><c:mrow><c:mi>s</c:mi></c:mrow></c:math>–<d:math xmlns:d="http://www.w3.org/1998/Math/MathML"><d:mn>2</d:mn><d:mrow><d:mi>p</d:mi></d:mrow></d:math> shells, we reach chemical accuracy for all atoms and properties with coupled cluster and full configuration interaction quantum Monte Carlo. Consistent total energies across disparate orbital sets and correlation solvers highlight the robustness of the TC workflow. Our study pushes benchmark-quality quantum chemistry into the <e:math xmlns:e="http://www.w3.org/1998/Math/MathML"><e:mn>3</e:mn><e:mrow><e:mi>d</e:mi></e:mrow></e:math> block without large-scale basis sets and opens a practical route for transcorrelation to strongly correlated molecules and materials hosting heavier transition metals.