molecule water_ethane { 0 1 O 0.523008077301 2.377244263218 0.000000000000 H 0.373560197839 2.946786409217 0.757230209944 H 0.373560197839 2.946786409217 -0.757230209944 -- 0 1 C 0.408607437691 -1.197764012732 0.000000000000 H 0.952547693882 -1.540225781408 0.877452261596 C -1.015225121462 -1.728012949788 0.000000000000 H 0.426479170162 -0.111980393109 0.000000000000 H 0.952547693882 -1.540225781408 -0.877452261596 H -1.034412040578 -2.815212546495 0.000000000000 H -1.560953900122 -1.388897418751 -0.877047401787 H -1.560953900122 -1.388897418751 0.877047401787 } set basis aug-cc-pVTZ set freeze_core true set guess sad set scf_type df set memory 50000mb sapt_energy = energy('sapt2+(3)dmp2', molecule=water_ethane)