I cannot say if it is a problem if some of your calculations used COORD=CART. I think it is best if you rerun a few of your calculations to see if the MP4 energy changes much upon using COORD=UNIQUE (as well as using the higher accuracy settings suggested by Pedro). If there are no significant changes, it could be that the problem with the geometry you posted is an isolated incident.
To save time, you could rerun these calculations with SDTQ=.F. and compare the individual contributions to the correlation energy instead of recalculating the full MP4(SDTQ) energies. Based on our earlier finding, I doubt that the problem will manifest itself only in the T part without causing deviations in other contributions.
On Wed Jun 26 '13 5:45pm, Xaiza wrote
>Dear Sir Thomas,
>I am very thankful to your insights, suggestions and for the effort of re-running my calculations. I will apply your suggestions in my recalculations. But I have a question sir. Would it be fine if some of my MP4 single point calculations have that keywords and some don't? That is, I'll only apply the keywords you have suggested on the molecules in which I have some problem with. I am bit worried about the energy differences that I would be obtaining, most especially since in some of my reactions, only in one molecule that I encountered this MP4 problem.
[ This message was edited on Wed Jun 26 '13 at 6:23pm by the author ]