Hello Sir,

Most of the above mentioned e.g: (formation of bond, decomposition of the bond, equilibrium constant, heat of reaction) can be pretty much done in any Quantum Chemistry software which includes DFT (Density functional theory). A list of these software is given here along with the licensing information: https://en.wikipedia.org/wiki/List_of_quantum_chemistry_and_solid-state_physics_software

By popular opinion Gaussian (Commercial) is probably the most user friendly and can be used as a black box (although I do not recommend that) even by people who are unaware of the fundamentals. Other softwares, like Turbomole (Commercial), GAMESS and ORCA are also equally good options.

Aside from the price of the softwares, I think the most important aspect is also to invest and/or to mange good computational resources. For most standard DFT calculations good CPU facility is a must.

I agree with Turbasu Sengupta and would add from my side few points:

1) description of "what has to be modelled" is still rather incomplete. Depending on it one would stick to sequence of DFT optimisations or to DFT-MD. Important part is size of the system, while systems around 100 nonhydrogen atoms can be handled rather fast and effective, 300 could already be a nasty problem. It can be simplified in few ways - QM/MM approach where chemically interacting groups (the one that have bond break and bond formation) are described with DFT and the rest of the system is handled with much cheaper approsch. Alternative to this could be semiempirical approach, however i would recommend to look not on canonical semiempirics but on Tight-Binding approaches (namely DFTB and GFN-XTB, both software are free) or may be "QM" method of Laikov (abbreviation should not be misunderstood with "quantum mechanics", it is available only in "Priroda" software that is free but has its own drawbacks). Among software for DFT-MD i would mention Terachem and periodic software like QuantumEspresso, VASP, Wien2K, CP2K, CPMD.

2) Its true that some software in quantum chemistry is pretty black-box, and entrance barrier to the field might be rather low. However "self-study" of this field quite often results in calculations that looks ok to the authors but are absolutely awkward, meaningless and facepalmy to the experts. I would really recommend to find someone who is knowing what he is doing and collaborate with this person/department (i do not suggest myself while i have enough of my own projects and this one is out of my sphere of interest, its just a friendly advice)

Hi Turbasu Sengupta and Dimitry Sharapa;

I appreciate very much your kind answer. You shared your valuable time with me.

I have a professor with experience in MD using MS beside myself. But, my case looks very complicated. It is challenging. I can access a cluster with 200 CPU.

It looks I need another person with Profesdionality in QD.

Thanks thanks and thanks

Dear Prof. Saeid Rajabzadeh,

For your purpose, I think "Schrödinger Suites" software, also, is a good choice.

About the software:

... With GPU-accelerated molecular dynamics simulations using the extremely efficient MD engine Desmond1, and the commercial OPLS3e force-field2,3, accurate prediction of polymer properties through atomistic simulation becomes feasible for even desktop computers. The Materials Science Suite provides chemical structure and polymer builders, a chemically adaptable cross-linking simulation module (Crosslink Polymers), automated thermophysical and mechanical response simulation modules (e.g. Thermophysical Properties, and Stress Strain), and analysis tools (e.g. MS MD Trajectory Analysis) allowing users to efficiently analyze single or multiple systems. Overall, the Materials Science Suite provides a unique and powerful advantage to both experienced polymer modelers and new-to-modeling scientists and engineers...

Best Regards

Khodadadi

Dear Saeid,

If you're looking at reactions in such large systems, using ab initio MD with DFT or DFTB is probably not going to be feasible. You may try to use ReaxFF, which has been developed specifically for dealing with chemical reactions in large complex systems. Some applications specifically to polymers:

https://www.scm.com/doc/Tutorials/Advanced/ReaxFF_polymers_bond_boost.html (looking at cross-linking polymers, no absolute reaction rates)

https://www.scm.com/doc/Tutorials/Advanced/ReaxFF_polymers_mechanical_properties.html (mechanical properties of epoxy polymers)

Kind regards,

Fedor

The chemkin may be useful for you.

in chemdraw 3D you can find a large calcul methods witch could help you