Dear Lammps Dev,
After spending some times in this research field, I have a doubt regarding DFT and MD
1. For examples, I have a structure of a crystal at 300K, if I minimize it at DFT, is it the structure still at the 300K configuration? (What I understand is minimization is at 0K).
2. Lets say I have a crystal and 300K and its potential, is it possible I heat it to a finite tempearature, e.g. 1000K, then I put it in DFT to find is electronics properties at 1000K?
Regards
min

Dear Lammps Dev,
After spending some times in this research field, I have a doubt regarding DFT and MD
DFT (i assume you are referring to density functional theory) and MD (= molecular dynamics)
describe two very different things. you can do MD with DFT (to derive the forces)
1. For examples, I have a structure of a crystal at 300K, if I minimize it at DFT, is it the structure still at the 300K configuration? (What I understand is minimization is at 0K).
no. however, only a complete minimization to the global minimum will
result in a true 0K structure. this is not easy. starting from a thermalized
configuration, a minimization usually leads into a local minimum. only
system with a very small number of degrees of freedom can always go
to the global minimum of potential energy.
2. Lets say I have a crystal and 300K and its potential, is it possible I heat it to a finite tempearature, e.g. 1000K, then I put it in DFT to find is electronics properties at 1000K?
yes and no. it will be an approximation. since forces in a classical model
are rarely identical with those from a DFT calculation. also, depending
on your material, you may have to consider thermal excitation of the
electrons in the process. a DFT based single point calculation is effectively
a minimization in a similar vain, as you were asking about in question 1
and thus compute the electronic structure of the ground state. if your
system is metallic or a semiconductor, that may not be sufficient. but
that is a question for a different mailing list.
you should also keep in mind, that at finite temperature
you donâ€™t have a single conformation that is representative
but rather an ensemble of configurations.
you probably should reread some chapters in your text books
on both electronic structure calculations and statistical mechanics.
cheers,
axel.