I wanted to dope Yttrium with 3+ valence in place of Germanium with 3+ in GaN structure. I tried to change the element in atomic positions at different points and then do relax and vcrelax. I am getting wrong lattice parameters after analysis of cell parameters. Can anyone guide on how to maintain the symmetry of the crystal while doping which is what I suspect is happening in my case.
N. Rajamanickam
Choose the dopant atom that has a similar ionic radius and electronegativity to the host atom. This will help to minimize the distortion of the crystal lattice. Use a supercell with a sufficiently large size to accommodate the dopant atom. The supercell should be large enough to ensure that the dopant atom does not interact with its periodic image. Replace only a small fraction of the host atoms with the dopant atoms. This will help to maintain the overall symmetry of the crystal structure. Place the dopant atom in a site that preserves the local symmetry of the crystal structure. In your case, you can replace Yttrium with 3+ valence in place of Germanium with 3+ in GaN structure. You can replace the Germanium atom with Yttrium in the same Wyckoff position. After replacing the atoms, relax the supercell using the relaxation scheme that is appropriate for your system. The relaxation scheme can be either "relax" or "vc-relax", depending on whether you want to keep the shape of the cell fixed or allow it to vary during the relaxation. Finally, analyze the cell parameters and ensure that they are consistent with the expected crystal structure. If the lattice parameters are wrong, it could be due to insufficient relaxation or an incorrect choice of the dopant atom.
Doping in Quantum Espresso supercell involves replacing some of the atoms in the original crystal structure with foreign atoms. To maintain the symmetry of the crystal structure while doping, it is essential to follow certain guidelines:
These guidelines should help you maintain the symmetry of the crystal structure while doping in Quantum Espresso supercell.
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