We study the potential energy curves and PESs of several test systems that have been studied in prior MS-PDFT papers. For all cases considered here except acetylene, CMS-PDFT has been shown to perform similarly to the more expensive XMS-CASPT2; hence, we use CMS-PDFT as a benchmark for those systems. For acetylene, we use XMS-CASPT2 as our benchmark because this system has not been studied previously with any MS-PDFT method. System-specific computational details including symmetry, basis set, number of states, active space electrons and orbitals, and reaction coordinates scanned are summarized in Table . For the spiro cation, XMS-PDFT data is taken from the supporting information of Ref 28.