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(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!
|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 ]