where the double excitation operator for the CIS-inactive electrons got split into an OS and SS component, each scaled with the parameter c OS T and c SS T , respectively, which were set to the SCS-MP2 ground-state values (c OS T = 6 5 , c OS T = 1 3 ,) In 2007, Rhee and Head-Gordon argued that SCS should also be applied to the direct term, which introduced two additional scale parameters c OS U and c SS U :[62]