I don't understand your problem. If you want to use PBE0 in Gaussian, just write PBE1PBE as keyword, see manual. If spin multiplicity is higher than 1, Gaussian automatically uses UKS formalism.
How can I use unrestricted version of PBE0-D3(BJ), wB97x-D or TPSSh for paramagnetic radicals? Thanks a lot!
PBE0-D3(BJ) is worth to try, which is very popular and robust in studying transition-metal complexes
I want to explore an alkyl radical capture by a Ni(II) species and that would form Ni(III) complex which would eventually undergo C(sp3)-C(sp3) reductive elimination. I wanted to see how the optimized transition state would look like for those functionals (not single points) in gaussian16, except for the fact that I tried UB3LYP-D3 and UM06-D3 already. Any help would be appreciated.