  Pseudopotential locality errors have hampered the applications of the
diffusion Monte Carlo (DMC) method in materials containing transition metals,
in particular oxides. We have developed locality error free effective core
potentials, pseudo-Hamiltonians, for transition metals ranging from Cr to Zn.
We have modified a procedure published by some of us in [M.C. Bennett et al,
JCTC 18 (2022)]. We carefully optimized our pseudo-Hamiltonians and achieved
transferability errors comparable to the best semilocal pseudopotentials used
with DMC but without incurring in locality errors. Our pseudo-Hamiltonian set
(named OPH23) bears the potential to significantly improve the accuracy of
many-body-first-principles calculations in fundamental science research of
complex materials involving transition metals.
