Extensive Total Energy and how to compare to NIST?
- MonteCarlo83
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6 years 4 months ago #445
by MonteCarlo83
Dear Cassandra-Community,
I have a question concerning the energy output in the property-file. In the documentation is written that the energy is given in kJ/mol and extensive. Is kJ/mol an extensive property? As far as I know it should be called intensive or have I misunderstood anything. When I compare total energies to values from NIST (for example), there are differences of several magnitudes. Do I make any mistakes in comparison or do I have to do any conversions?
Thank you very much in advance and best regards
Mark
I have a question concerning the energy output in the property-file. In the documentation is written that the energy is given in kJ/mol and extensive. Is kJ/mol an extensive property? As far as I know it should be called intensive or have I misunderstood anything. When I compare total energies to values from NIST (for example), there are differences of several magnitudes. Do I make any mistakes in comparison or do I have to do any conversions?
Thank you very much in advance and best regards
Mark
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- ejmaginn
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6 years 4 months ago #446
by ejmaginn
Mark,
This is a confusing issue for many simulation packages. You are correct that kJ/mol is intensive. Cassandra's energy output is extensive in the sense that if you double the number of molecules, you will double the magnitude of the energy. So to obtain "true" kJ/mol, simply divide the value Cassandra give you by the number of molecules in your system. I hope that when you do that, you will get good agreement with NIST. Let us know. And we should probably clean up the documentation of this.
This is a confusing issue for many simulation packages. You are correct that kJ/mol is intensive. Cassandra's energy output is extensive in the sense that if you double the number of molecules, you will double the magnitude of the energy. So to obtain "true" kJ/mol, simply divide the value Cassandra give you by the number of molecules in your system. I hope that when you do that, you will get good agreement with NIST. Let us know. And we should probably clean up the documentation of this.
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- MonteCarlo83
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