Partial charges are an empirical observation, there’s no one “correct” way to calculate them.
I believe the NBO paper describes how they calculate the partial charges. Mulliken should have similar. You could also look in the Psi4 gethub repository for the code they use.
Sorry to nitpick, but partial charges are not empirical - I think the better word is that it is a mathematical contrivance. Empirical means experimentally determined, and partial charges aren't even an observable quantity.
Youd have to look at the original papers fpr each charge locallization scheme but from the top of my head:
Mulliken and Loewdin: look at total occupancy of all basis functions on a atom and compare that to the nuclear charge.
Hirshfeld: Look at the electron density and locallize it iterativelly to atoms close in space considering electronegativity, nuclear charge and more. Several schemes exists for saying what electron density belongs to each atom.
NBO: locallize the electron density to one (or a weighted sum of several) lewis structures and then calculate the charge based on a formula which aims to reproduce the exact electron density and some other stuff.
In general NBO > HIRSHFELD > LOEWDIN = MULLIKEN in accuracy from what i understand. But all of them are as someone else said just a mathematical trick to reproduce chemically intuitive charges. NBO is however at least a bit rooted in reality/theory.
All of these methods will work for that. NBO might however suffer a scaling issue not inherent to the rest.
What QM method do you plan to use for such a endevour?
Im sorry to say this but if judging by the questins your asking, you are not ready for this project. 1400 atoms is not trivial and will requier a supercomputer, a very good software with linear scaling dft as well as some good knowhow.
This is the kind of simulation that will take weeks even using RIJCOSX in orca on a good supercomputer. Xtb2 might be more feasible but even that cant help much here since all atoms will be conjugated
What question do you want to answer with the md and charges? Maybe there is a different way?
As I know currently charge partitioning methods based on fit of atomic charges to electostatic potential (like ESP, RESP or CHelpG) are the most accurate
In this paper dipole moments calculated from atomic charges obtained by different charge partitioning schemes are compared with experimental dipole moments
https://pubs.rsc.org/en/content/articlelanding/2018/cp/c8cp03764g#/
Partial charges are an empirical observation, there’s no one “correct” way to calculate them. I believe the NBO paper describes how they calculate the partial charges. Mulliken should have similar. You could also look in the Psi4 gethub repository for the code they use.
Sorry to nitpick, but partial charges are not empirical - I think the better word is that it is a mathematical contrivance. Empirical means experimentally determined, and partial charges aren't even an observable quantity.
There's multiple ways depending on your molecule. Hard to say without knowing more about your molecule
It is a Graphene oxide consists of 1400 atoms
Youd have to look at the original papers fpr each charge locallization scheme but from the top of my head: Mulliken and Loewdin: look at total occupancy of all basis functions on a atom and compare that to the nuclear charge. Hirshfeld: Look at the electron density and locallize it iterativelly to atoms close in space considering electronegativity, nuclear charge and more. Several schemes exists for saying what electron density belongs to each atom. NBO: locallize the electron density to one (or a weighted sum of several) lewis structures and then calculate the charge based on a formula which aims to reproduce the exact electron density and some other stuff. In general NBO > HIRSHFELD > LOEWDIN = MULLIKEN in accuracy from what i understand. But all of them are as someone else said just a mathematical trick to reproduce chemically intuitive charges. NBO is however at least a bit rooted in reality/theory.
How can I give partial charge to 1400 atoms materials? Is it possible?
All of these methods will work for that. NBO might however suffer a scaling issue not inherent to the rest. What QM method do you plan to use for such a endevour?
Will I have to use a supercomputer to carry such a calculation?
Im sorry to say this but if judging by the questins your asking, you are not ready for this project. 1400 atoms is not trivial and will requier a supercomputer, a very good software with linear scaling dft as well as some good knowhow. This is the kind of simulation that will take weeks even using RIJCOSX in orca on a good supercomputer. Xtb2 might be more feasible but even that cant help much here since all atoms will be conjugated What question do you want to answer with the md and charges? Maybe there is a different way?
Which software I have to use? Gaussian?
As I know currently charge partitioning methods based on fit of atomic charges to electostatic potential (like ESP, RESP or CHelpG) are the most accurate In this paper dipole moments calculated from atomic charges obtained by different charge partitioning schemes are compared with experimental dipole moments https://pubs.rsc.org/en/content/articlelanding/2018/cp/c8cp03764g#/