| Re: Inconsistent forces between rhombohedral and hexagonal unit cells ( No.1 )|
- Date: 2023/08/22 14:23
- Name: Naoya Yamaguchi
Although the atomic positions are found to be shifted by comparing one structure with the other (e.g. `3.03990` and `3.03991`), issues like this often occur when the given unit cell is slender, and it may be caused by numerical errors coming from description of the density gradient.
In my experiences, there are several workarounds.
1. Avoid `GGA-PBE` for `scf.XcType`
2. Use a denser real space grid through `scf.Ngrid` instead of `scf.energycutoff`
As an example of `scf.Ngrid` in a slender cell, you can refer to No. 8 of https://www.openmx-square.org/forum/patio.cgi?mode=view&no=2649 .
3. Not to use the slender cell
| Re: Inconsistent forces between rhombohedral and hexagonal unit cells ( No.2 )|
- Date: 2023/08/22 15:05
- Name: Hiroaki Tanaka
- Dear Naoya Yamaguchi,
Thank you for your prompt reply.
I follow your advices and find that denser Ngrid works well.