How to determine the k offset to obtain the converged result

[sandf]

TL;DR Summary

How to determine the k offset to obtain the converged value for physical property in the first-principles calculation.

Dear all,
As I know, in the calculation of physical property of solid, e.g. optical property. The k offset is often used to generate the k-grid to avoid no enough weight at high symmetry k points in the calculations. For example, for GaAs, an offset of 0.5 0.5 0.5 could be used to calculate the second-harmonic generation (second-order polarizability). Alternatively, an arbitrary offset such as 0.25 0.5 0.625 could be used.
Now my question is how to determine whether I have selected an appropriate k offset or not. By comparing with experimental results, or others?Youzhao Lan
Zhejiang Norm. Univ.
China

 

[eljose79]

Dear Youzhao Lan,

Thank you for bringing up this important question. The selection of an appropriate k offset in solid state calculations is crucial in accurately predicting physical properties such as optical properties. It is a common practice to use a k offset in order to generate a k-grid that has enough weight at high symmetry k points, as you mentioned.

There are a few ways to determine whether the selected k offset is appropriate or not. One way is to compare the calculated results with experimental results, if available. If the results are in good agreement, then it is likely that the selected k offset is appropriate. However, it is important to note that there may still be some discrepancies between the calculated and experimental results due to factors such as approximations in the calculation method.

Another way to determine the appropriateness of the k offset is to compare the results obtained using different k offsets. If there is a significant difference in the results, it may indicate that the selected k offset was not suitable for the calculation. In this case, it may be necessary to try different k offsets or even increase the k-grid density to obtain more accurate results.

Additionally, it is always helpful to consult with other experts in the field or refer to literature for guidance on selecting an appropriate k offset for a specific material or property. Collaborating with other researchers can also provide valuable insights and help in determining the best approach for your calculations.

I hope this helps answer your question. Best of luck with your research.