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23.8 Spin-component scaled MP2 (SCS-MP2)

The spin-component scaled MP2 energy as proposed by Grimme (J. Chem. Phys. 118, 9095 (2003)) is printed automatically using the default scaling factors (1.2 for antiparallel spin, 1/3 for parallel spin). These factors can be modified using the options SCSFACS and SCSFACT, respectively, i.e.


The SCS-MP2 total energy is stored in the variable EMP2_SCS. Gradients and first-order properties can be computed for SCS-MP2 by setting the option SCSGRD=1. This only operational for density fitted MP2 and local MP2 methods, i.e. using

DF-MP2,[DF_BASIS=fitbasis],SCSGRD=1,[ SCSFACS=facs], [SCSFACT=fact]

followed by FORCES or OPTG. In these cases, the SCS-MP2 total energy replaces the MP2 total energy in the variable EMP2. Expectation values can also be computed with DF-SCS-MP2, where the SCS-MP2 density matrix is used instead of the MP2 density matrix (see section 23.1). For DF-LMP2 see section 32. 2018-01-22