I have been optmising Si atom (lattice constant), but I am facing an issue with defining an accurate PAO basis block or/and the Eshift!!! I did look through some websites but with the data for PAO basis block I got, I couldn't managed to get the more exact lattice constant for Si with GGA-PBE. I know, silicon is some basic one and well defined. How to get more accurate value of lattice constant by managing the PAO basis block Rcut or using the Eshift parameter ?
To perform a convergence test for the E shift parameter, follow these steps:
Choose a system and perform a SIESTA calculation with a default E shift value.
Reduce the E shift value by a factor of two and perform another SIESTA calculation.
Repeat the above step until the E shift value is small enough (e.g. 1 meV).
Plot the total energy of the system as a function of the E shift value.
The E shift value is considered to be converged when the total energy changes by less than a certain tolerance (e.g. 1 meV) as the E shift value is reduced further.
It's recommended to use a smaller tolerance for the E shift convergence test in SIESTA when calculating systems with large band gaps.
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