Understanding DFT to Calculate Potential Energy of Atoms

In summary: You could in principle do it by solving the equations of motion for the solid as a whole, but that would be a very long and expensive calculation. In summary, you can use DFT to calculate the potential energy of atoms in a structure. You can do this by using Vasp or another package to calculate the potential energy of the atom. Alternatively, you can replace an atom in the structure by a ghost atom with the same basis set but zero nuclear charge.
  • #1
wkxez
6
0
I am a freshman in DFT calculation. I don't understand the DFT method clearly,but I want to use DFT to do some calculations.
My question is that how how can I get the potential energy of each atom in a structure using DFT package ,which I have done by using classical MD method in Lammps(the command: compute 1 all pe/atom ,Lammps manual :The per-atom energy is calculated by the various pair, bond, etc potentials defined for the simulation. If no extra keywords are listed, then the potential energy is the sum of pair, bond, angle, dihedral,improper, and kspace energy.).
I want to know how can I do such a calculation.Please give some suggestions.
 
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  • #2


I now know that i can get the force F of each atom from the results of vasp relaxation calculation .In the classical theory,F= dU/dr(U is the potential energy),,so if it's possible to get the potential energy from the VAsp or other package calculation?
 
  • #3


The notion of energy per atom is ill defined for a non-crystalline material. IF you are modelling a crystal , you simply divide the total energy by the number of unit formulas of the crysta.
 
  • #4


Useful nucleus said:
The notion of energy per atom is ill defined for a non-crystalline material. IF you are modelling a crystal , you simply divide the total energy by the number of unit formulas of the crysta.


Thank you for your reply,Why is it ill defined for non-crystalline material? And you may misunderstand my question. I want to get the relative potential energy of each atom in a structure,not energy per atom.
 
  • #5


wkxez said:
Thank you for your reply,Why is it ill defined for non-crystalline material? And you may misunderstand my question. I want to get the relative potential energy of each atom in a structure,not energy per atom.

In an infinite solid this is difficult, in a molecule you can in principle remove that atom from the calculation and compare the energy of the molecule with and without the atom. In practice there is a problem called basis set superposition error, and you may have to replace the atom by a ghost atom with the same basis set but zero nuclear charge.
For a solid you would have to consider probably some large super cell.
 

1. What is DFT and how does it calculate potential energy of atoms?

DFT (Density Functional Theory) is a computational method used to study the electronic structure and properties of atoms and molecules. It uses quantum mechanical principles to calculate the ground state energy of a system. This energy can then be used to determine the potential energy of atoms within the system.

2. What are the advantages of using DFT over other methods for calculating potential energy?

DFT is advantageous because it is relatively computationally efficient and can be applied to a wide range of systems, including large molecules and solids. It also accounts for electron-electron interactions and can provide accurate results for both ground and excited states.

3. What information can be obtained from DFT calculations regarding potential energy of atoms?

DFT calculations can provide information about the electronic structure, stability, and reactivity of atoms and molecules. It can also predict various properties such as bond lengths, bond energies, and dipole moments.

4. Are there any limitations to using DFT for calculating potential energy?

Although DFT is a powerful tool, it has some limitations. It is based on approximations and can only provide accurate results if the system is well-described by the chosen functional and basis set. It also cannot capture dynamic effects, such as temperature and time-dependent phenomena.

5. How can DFT calculations be validated and verified?

DFT calculations can be validated by comparing the results with experimental data or more accurate theoretical methods. Additionally, the accuracy of DFT can be improved by using more sophisticated functionals and increasing the size of the basis set.

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