Using ReaxFF in ionic systems

Dear LAMMPS users,

I have a molecular system containing metal ions in which some reactions occurred. Can I use ReaxFF force field defined in LAMMPS software to simulate such a system? Can this force field be used in ionic reactive systems?

Regards,

Mina

That depends on finding a suitable parameterization.

Please check out Adri van Duin’s homepage and the published literature.

Axel

Dear Dr. Kohlmeyer,

Thank you for your reply. Actually, my question is about using ReaxFF in ionic systems. I want to immerse Zn2+ and SO42- in a water system containing protein. As ReaxFF uses QEq charge method,How can I use it in an ionic system? I mean how can I define atomic charges of ions as the force field not to recognize the ions as metals? Because as you know, in data file of ReaxFF force field all of the charges are considered to zero. I appreciate your help.

Regards,

Mina

Dear Dr. Kohlmeyer,

Thank you for your reply. Actually, my question is about using ReaxFF in ionic systems. I want to immerse Zn2+ and SO42- in a water system containing protein. As ReaxFF uses QEq charge method,How can I use it in an ionic system? I mean how can I define atomic charges of ions as the force field not to recognize the ions as metals? Because as you know, in data file of ReaxFF force field all of the charges are considered to zero.

your assessment is not correct.

practically no ion in solution has an exactly integer charge. especially not divalent or trivalent ions and particularly not in solution. this is just elementary inorganic chemistry knowledge. you can confirm this with quantum chemical calculations.

in reaxff charges are not zero, they are dynamically computed on-the-fly using the charge equilibration method. if you have a properly parameterized reaxff parameter set, you should get a charge distribution that approximates what you get from quantum chemical calculations. that is what parameter sets are parameterized for. it appears to me, you have to learn a bit more about how reaxff works before you should do any serious calculations with it.

axel.

Dear Axel,

Thank you for your beneficial explanations. I mentioned in my last Email that ReaxFF uses QEq charges. If I concluded correctly, one can use Reax force fields in an ionic system if the parameter set are parametrized precisely, because this force field distinguishes and adjusts the charges of ions itself. Please correct me if I am not right. Thank you so much,

Best regards,

Mina