Meaning of total ground state energy in periodic DFT calculations

In summary, the total ground state energy in periodic DFT calculations is the lowest energy state of a system and is determined by solving the Kohn-Sham equations and minimizing the total energy functional. It is influenced by factors such as the choice of exchange-correlation functional, system size, and convergence criteria. This energy is important for predicting and understanding the behavior of a system and can be compared between different systems by calculating the energy per unit cell or per atom.
  • #1
Derivator
149
0
Dear all,

periodic DFT codes (e.g. VASP) effectively simulate an infinite crystal due to the periodic boundary conditions. However, the energy value that one obtaines at the end of a simulation if finite. Frankly, I'm quite confused right now.

Is the energy to be understood 'per unit cell'? Why is the energy value not infinite?

Cheers,
derivator
 
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  • #2
Yes, it is per unit cell.
 

FAQ: Meaning of total ground state energy in periodic DFT calculations

1. What is the total ground state energy in periodic DFT calculations?

The total ground state energy is the lowest energy state of a system in a periodic density functional theory (DFT) calculation. It takes into account the interactions between all particles in the system and represents the overall stability of the system at a specific geometry.

2. How is the total ground state energy calculated in periodic DFT calculations?

The total ground state energy is calculated by solving the Kohn-Sham equations, which describe the electronic structure and energy of a system in DFT. This involves minimizing the total energy functional, which is a sum of the kinetic energy, electron-nucleus interaction, and electron-electron interaction energies.

3. What factors influence the total ground state energy in periodic DFT calculations?

The total ground state energy is influenced by the choice of exchange-correlation functional, the size of the system, and the convergence criteria used in the calculation. It is also affected by the type and number of atoms present, as well as the geometry and symmetry of the system.

4. Why is the total ground state energy important in periodic DFT calculations?

The total ground state energy is important because it provides a measure of the stability and energetics of a system, which can be used to predict and understand its behavior. It is also used to calculate other properties, such as band gaps and reaction energies, which are crucial in materials science and chemistry.

5. How can the total ground state energy be compared between different systems in periodic DFT calculations?

The total ground state energy can be compared between different systems by calculating the energy per unit cell or per atom. This allows for a more direct comparison, as the total energy of a larger system would naturally be higher than that of a smaller system. Additionally, the energy difference between different calculations can also be compared to determine which system is more stable.

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