include procedures geometry={O; !Z-matrix for water H1,O,R; H2,O,R,H1,THETA} basis=vtz !use VTZ basis R=0.96 Ang !start bond distance Theta=104 !start bond angle hf mp2 optg !optimize MP2 energy mp4 !do single-point MP4 at MP2 geometry ccsd(t) !do single-point CCSD(T) at MP2 geometry