Hello again, I'm very sorry I forgot to put in the tail of the input file. Benj PROC UCCSDT={ basis=6-31g*; {hf; start,atden; wf,15,1,1} basis=6-311g**; {hf; wf,15,1,1} basis=aug-cc-pvdz; {hf; wf,15,1,1} {uccsd(t); wf,15,1,1} }