I've carried out some single point B3LYP calculations and extracted the energies by searching "SCF Done" in the log file, in this case the resulting values match up with the resulting energies found on GaussView.
I carried out the same calculations using MP2 but I've found that the result values from GaussView do not match up with the "SCF Done" line but rather the "E2 =" line. What is the source of this difference?
Something tells be that searching the "SCF Done" line is the incorrect way to extract energies, so if anyone can show me the correct way to extract energy values from these files, I'd be very grateful.
In B3LYP calculations "SCF Done" gives the energy, but in MP2 "SCF Done" is the HF energy while "E2 = " is the perturbation energy achieved with MP2 method.
There are two ways to find the energy values,
1 Simply open log file and find individual energy value
2 By opening log file through any software (e.g. Gabedit , Chem Bio-Ultra 3D) which which will give list of energies calculated through view energies tool bar.
Thank you both for the responses but I am still looking for more information. How do I extract the relevant energy values that I need to make comparisons between the B3LYP energies vs MP2 energies (do I use the HF energy or perturbation energy?).
Also, I have a series of log files to which I would like to find the energy values in a text editor (Notepad++) to import into excel. I do not want to have to open each log file in a software package one by one to exact the energy values.
I believe the E2 energy corresponds to just the correlation energy, the quantity you are looking for is probably the HF SCF energy plus the correlation energy (the MP2 total energy).
I think this is reported as EUMP2 in Gaussian, but I don't have a file handy to check.
Grant Hill is correct -- search for the "EUMP2" and that is the total energy you need, which is the sum of the HF energy ("SCF Done" line) + E2, the second order perturbation correction.
"SCF Done " is the energy calculated by Hartee fock. The MP2 energy printed in form of EUMP2 and MP2= in the end of log file. In order to extract the MP2 energies grep "EUMP2" *.log files
Thank you very much everyone for your contribution! One last question, this is regarding to the thermal correction at 298K.
For my B3LYP data I basically sum the "SCF Done" value from a single point calculation to the "Thermal correction to Enthalpy" to get the 298K energy values. In essence (E0+Hcorr). I do this because I use a larger basis set for the single point energy calculations than my frequency calculations.
Can I treat my MP2 calculations in the same manner? In this case Hcorr="Thermal correction to Enthalpy" from my B3LYP frequency calculations and E0="EUMP2" from my MP2 single point energy values.
HF energy is obtained at the very end of the calculation, like this
HF=-819.3448754 after "State=1-A".
In the Gaussian09 online manual there is an example for the energy of perturbation methods. For MP2 it is labelled EUMP2. In the final summary of the job (the block before the quote) it is labelled as "MP2=..."
A very good concise and well explained manual for thermochemistry in gaussian can also be found on their website. It includes worked examples, but to make things short, you add the thermal corrections to the MP2 energy.
http://www.gaussian.com/g_tech/g_ur/k_mp.htm
http://www.gaussian.com/g_whitepap/thermo/thermo.pdf
Article Thermochemistry in Gaussian
Patrick Batoon, you don't need to open each file one by one to extract the data.
You can just type [grep "E2 = " *] and [grep "SCF Done" *] on you terminal to get those data.
If you don't use a Unix-like OS, install a Linux emulator for Windows such as Cygwin to obtain that useful command.
Today I leave from the house and I shall be away from February, 20th till March, 26th, 2015
Thanks for the response Francesco, but I failed to mention that I don't open the file one-by-one. My method for extracting data is opening all files with Notepad++ and searching for the correct keyword. This is pretty much the same as having the data reported on the unix terminal when using grep "E2="* and *SCF Done"*
The energy you need is printed in the output. It is not printed to the full decimal order but maybe that's all the certainty you need. If not, you have probably already discovered this.
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