Transcorrelated Theory for Transition Metal Atoms

TL;DR

This paper demonstrates that transcorrelated Hamiltonians combined with pseudopotentials can accurately compute ionisation and excitation energies of transition-metal atoms, enabling benchmark-quality results with reduced computational cost.

Contribution

It introduces a transcorrelated approach that achieves high-accuracy quantum chemical calculations for transition metals without large basis sets or extensive extrapolations.

Findings

Achieves chemical accuracy for transition-metal atoms using compact basis sets.

Provides consistent total energies across different orbital sets and correlation methods.

Enables benchmark-quality calculations in the 3d transition metal series efficiently.

Abstract

We benchmark ionisation and excitation energies of transition-metal atoms Sc-Zn with a transcorrelated Hamiltonian combined with pseudopotentials. The similarity transformed Hamiltonian provides compact 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 (3s 3p) valence and freezing only 1s-2p 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 highlights the robustness of the TC workflow. Our study pushes benchmark-quality quantum chemistry into the 3d block without large-scale basis sets and opens a practical route for transcorrelation to strongly correlated molecules and materials hosting heavier transition metals.