Calculated value of chemical shift of Cu in VASP first principles

U = 0 eV

U = 4 eV

U = 7.5 eV

U = 10 eV

PBE

ISO_SHIFT

PBE + U

ISO_SHIFT

PBE + U

ISO_SHIFT

PBE + U

ISO_SHIFT

Cu₂Se

647.9390

−236.8034

−647.5071

−874.4668

Cu₂S

598.7500

−90.2254

−537.0861

−775.6825

Cu₂Te

543.2066

−124.2206

−522.5469

−740.6468