[molpro-user] Mp4 energies

[Lorenzo Lodi]

I would like to understand the difference between MP4(SDTQ) and 
MP4(SDTQ(T)) energies. I couldn't find any information about it in the 
manual.

For example, consider the following super-minimal input:
geometry = { Ne }
basis=cc-pVDZ
{RHF}
{MP4}

I get:
Reference energy                   -128.488775551740
MP4(SDQ) singlet pair energy         -0.116731030994
MP4(SDQ) triplet pair energy         -0.072089939641

MP4(SDQ) correlation energy          -0.189092580027
Triples (T) contribution             -0.001182379164
Total correlation energy             -0.190274959190

MP4(SDTQ) total energy             -128.677868131767
!MP4(SDTQ(T) total energy          -128.679050510931

Which value should be more accurate, SDTQ or SDTQ(T)? (I suspect the latter)

Thank you.

Lorenzo