Tuning the charge-transfer energy in hole-doped cuprates

Chemical substitution, combined with strain, allows the charge-transfer energy in hole-doped cuprates to be broadly tuned. We theoretically characterize the structural and electronic properties of the family of compounds $R_2$CuO$_2$S$_2$, constructed by sulfur replacement of the apical oxygens and rare earth substitutions in the parent cuprate La$_2$CuO$_4$. Additionally, the enthalpies of formation for possible synthesis pathways are determined.