Hello men and brethren,
I started studying Material studio (MS) recently having commenced Gaussian 09 (DFT calculations) previously. What I noticed almost discouraged me from continuing with MS. Hence, I decided to clear my curiosity by putting up these queries.
When different modules (e.g. Dmol3, Forcite, DFTB+ ) is used in MS to optimize a material (e.g. Bisphenol), I noticed that the output results contain different values of Initial and Total Energy. Why is it so? I planned to obtain Binding Energy, Heat of formation, Enthalpy, and Gibb's free energy from my calculation. Which modules can give these outputs.
Please kindly clear my curiosities.
Thank you.
Shed.
Every basis set and software use different algorithms and force fields to compute the geometry of molecule of interest, so different outputs are generated. First, we have to perform the conformational analysis of molecule. After getting most stable conformer, it should be taken for further experiments or validation.
Thanks for your response Naresh Kumar . Still in the dark. Please kindly throw more light.
Thank you Travis P Pollard
for your kind response. However, how can I identify which energy is which (eg. binding energy, or Gibb's free energy) from the various output results because they are not explicitly specified as either free energy, enthalpy or binding energy. I look forward for more response.Thank you.
In electronic structure calculations there are difficult to get the absolute value of the total energy as it depends on the numeric and algorithm implementation, software development (even on the linker-compilator and programing language), approximations and calculation schemes (Core-Valence separation, Basis Set/Plane Waves/ Projector Augmented-Wave, Effective Core Potentials/ Pseudo-Potentials, Exchange and Correlation Potentials, open/periodic system); rather the binding energy is relevant. Therefore, different calculation schemes and software will give different total Energy, Gradients and Hessian of the energy, and by consequence different structural (geometries) and electronic properties.
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