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I want to calculate defect formation energy for a substitutionally doped system (bulk) in a charged state. Is it possible to do such calculation using SIESTA code? If yes, what changes do I make in my input fdf file for that?

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1 Answer 1

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Yes, it is possible to calculate defect formation energy for a substitutionally doped system in a charged state using the SIESTA code.

To calculate the defect formation energy, you need to consider the total energy of the doped system with the defect, as well as the total energies of the pristine host material and the dopant in its isolated form. The defect formation energy can then be calculated using the following equation:

E_form = E_defect + n_host * E_host - n_dopant * E_dopant

Where:

E_form is the defect formation energy.
E_defect is the total energy of the doped system with the defect.
n_host is the number of host atoms in the doped system.
E_host is the total energy of the pristine host material.
n_dopant is the number of dopant atoms in the doped system.
E_dopant is the total energy of the dopant in its isolated form.

To perform such calculations in SIESTA, you would need to modify your input fdf file accordingly. Here are the key changes you should consider:

  1. Specify the atomic positions and lattice parameters for the doped system, including the defect and the dopant atoms.
  2. Set up the appropriate electronic structure calculation parameters, such as the basis set, k-point grid, and convergence criteria. These settings will depend on the specific system and accuracy requirements.
  3. Include the appropriate pseudopotentials for the elements involved in your system, including the dopant atom and any other relevant elements.
  4. Set the initial charge state for the dopant atom by specifying the occupation or number of electrons. This can be done using the OccupationFunction or OccupationNumber keywords in the SystemLabel block.
  5. Specify the total number of atoms in the doped system (NumberOfAtoms keyword) and the number of electrons in the system (NumberOfElectrons keyword).
  6. Calculate the total energy of the doped system with the defect by performing a self-consistent calculation using the SCF block.
  7. Perform separate calculations to obtain the total energies of the pristine host material and the dopant in its isolated form. These calculations should be done with the defect and other dopants removed from the system.

Use the obtained total energies to calculate the defect formation energy using the equation mentioned earlier.

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