I want to calculate the formation energy of benzene, naphthalene, coronene. Is it measured in term of per atom (atom-1) ?
the procedure should be same as with any other computational method.
you calculate the total energy of say Benzene and then you calculate the total energy of isolated carbon and hydrogen.
then use simple arithmetic to get the formation energy.
Do you mean that you want to compute the heat of formation as measured by experiment? Heat of formation of a molecule is measured compared to elements in their standard states. In this case graphite and H2 at 273K and 1atm. Is this what you need to do?
DFT does much better on relative energies than on absolute heats of formation. It is easier to get the experimental heat of formation of a few compounds, and then compute the reaction energy between those and benzene. Then you compute the heat of formation of benzene based on the differences.
In this guide you find the method to obtain heat of formation by gaussian software, which is the same in related electronic structure programs.
regards!
Can anyone suggest how can we calculate formation energy of a bulk crystal from the results obtained from wien2k?
Please suggest a link or any papers.
Kind regards
THE ENERGY FORMATION FOR EACH ALLOY IS OBTAINED WHEN DOING THE MINIMISATION IN THE WEB PAGE WE HAVE VOLUME, BULK MODULUS, PRESSURE DERIVATIVE AND THE MINIMAL ENERGY THIS REPRESENT THE MINIMAL ENERGY FOR FORMATION
Hello friends!
Calculation of formation energy ( if it means standard enthalpy (SEF) of formation for a molecule as Dr George Fitzgerald mentioned) using DFT is not straightforward. The procedure presented by Sen calculates atomization energy not SEF.
Dear Rakesh and Chandra,
Enthalpy of molecules/atoms is calculated by default using Gaussian software provided 'freq' keyword to it. And ofcourse prior to freq, you need to optimize the geometry first. However, these energies would be in negative and you can read about it that why does it give negative energy.
Coming to the enthalpy of formation, there is formula given in Gaussian thermochemistry whitepaper by which one can easily undergo/perform for the desired calculation. Here is the link:
http://gaussian.com/g_whitepap/thermo/thermo.pdf
If one wants a better accuracy then they can go for compound methods, e.g., G4 or G3MP2 methods, however, DFT (B3LYP etc.) also gives good accuracy but not as accurate as compound methods.
Gaussian software only provides energies in hartrees which further can be converted into desired units, e.g., kcal/mol, kJ/mol, eV etc.
You can calculate that via applied the Gaussian program ( any version) for the specific material.You will find the formation energy of ( Enthalpy and Gibbs)in the end of output results of your run. Then it can be used the simple formula to find the Entropy formation energy also.
If you want to obtain the value of heat of formation firstly you can obtimize the structure of any new molecule by using DFT in hyperchem, then you can cheque the properties option and you will find electronic energy, total energy ,entropy binding energy and heat of formation as well.
you can calculated Heat of formation or any energy ( Total energy, Binding energy, LUMO-HOMO energy gap and others) by using Heperchem program or Gaussian program after done geometry optimization then run energy. The results get from output file.
Hello everyone,
I want to restart this discussion for calculation of chemical potential. Do any experts have experience to calculate chemical potential using VASP or EQ (first principle method) ? what is the basic way to do.
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