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'Abnormal Energy' obtained in MP4 single point energy calculation
Hello everyone!

I am currently running an MP4 single point energy calculation (basis set: 6-311++G**) on a few hydrocarbons using Firefly version 7.1.G in one of the PCs in our laboratory. The geometry I used for the single point energy calculation was the equilibrium geometry I obtained from my MP2 optimization calculation using the same molecule. On some of my molecules examined at MP4, I found out that the energy calculated was 'abnormally' large(i.e. the absolute value of the energy calculated) that my succeeding calculations (i.e. enthalpy of reaction, enthalpy of activation, etc. ) doesn't make any sense at all. I checked my input files, they were all the same. I just changed the geometry. Shown below is the fraction of my result wherein the energy I label as 'abnormal' is reflected.

RESULTS OF MOLLER-PLESSET 4TH ORDER CORRECTION ARE

E(RHF)       =      -309.9452940908

E(D,2)       =        -1.1646736559
E(MP2)       =      -311.1099677467

E(D,3)       =        -0.0698223432
E(D,2+3)     =        -1.2344959991
E(MP3)       =      -311.1797900899

E(S,4)       =        -0.0443751557
E(D,4)       =      -105.3701897285
E(D,2+3+4)   =      -106.6046857276
E(T,4)       =        -0.0706244480
E(R+Q,4)     =         0.0297425817
E(SDTQ,4)    =      -105.4554467506
E(SDTQ,2+3+4)=      -106.6899427497
E(MP4-SDTQ)  =      -416.6352368404

..... DONE WITH MP4 ENERGY .....

I also attached the output file of this calculation. What might be the problem in this calculation? Can I ask for suggestions on how to improve/solve such? Any help is highly appreciated. Thank you in advance!

Regards,
Xaiza

 This message contains the 1114 kb attachment [ single_point.log ] output file containing 'abnormal energy'

[ This message was edited on Wed Jun 26 '13 at 2:49pm by the author ]

Wed Jun 26 '13 2:49pm